I've never had this problem with beardies, but I have pretty extensive experience in taming wild herp species which are not nearly so naturally friendly as beardies, so this may be of some help. (I used to live in the woods and my cats, though I tried to keep them in, would get out and then catch wild reptiles, mostly alligator lizards, Western fence lizards/bluebellies, and garter snakes. Of course if I or anyone else saw them doing this we'd take the reptile away immediately. For some reason they never seemed to get birds or other animals, only reptiles. At least not where we could see it. Anyway, if the reptile was at all injured, we would usually end up keeping it because it would just get eaten by some other predator if we let it go hurt. Every single one of those reptiles ended up becoming beloved pets which stayed with us for many years. I've had more alligator lizards in my life than beardies!)
First of all, you can't let them intimidate you, because once they sense that biting works to drive you away, they'll keep doing it as often as possible. Whereas if it DOESN'T work, most of them will give up pretty quickly. Even wild lizards like alligators and bluebellies are smart, and beardies are much smarter than either of those two.
Continual contact and patient, gentle persistence help a lot. So does not permitting them to hide from you. Yes, this will stress them at first and if there are ANY health issues in the dragon it's a bad idea, but if the ONLY issue with this dragon is its fear of people, then it needs to be denied a hide for the moment. Ripping it out of its hide and forcing it to interact is much more stressful than simply not having one to begin with, and having to confront at least the sight of people all the time.
Is it possible that this dragon was neglected or abused in its previous place? It may have never been handled before, or it may have been handled roughly and ignorantly. You will therefore need to teach it that handling is a safe, pleasant thing, and not a threat. Particularly if you are working against past negative experiences this can take a long time. PATIENCE is going to have to be your watchword here. I cannot emphasize this enough. You are VERY LUCKY to be working with a beardie and not, say, an iguana or a wild reptile like the ones I mentioned previously. Even if your beardie has had bad experiences in the past, it will develop trust MUCH more quickly than pretty much any other lizard species I am aware of. That's one of the interesting things about beardies that makes them special.
Anyway, make a point of putting your hands in the cage a lot WITHOUT picking up, touching, or interacting with the dragon in any way. Make up reasons to go in there. Rotate the salad more frequently than necessary for instance (you can put it in the fridge if it's still good so it doesn't go to waste, and put the same salad back in when you rotate them again, or use it to gutload feeders.) This will help them see that your hands do not necessarily equate with being grabbed at and removed from the only relatively safe environment the dragon knows.
Yes, they will hiss and run and act very uncomfortable when you try to interact. This is because they are! They are afraid of you and fear is no fun. There is NOTHING you can do about that right now. It's very difficult, I know, when they seem like they would just rather be left alone. But with gentle, patient persistence, I have transformed wild lizards and snakes into pets that loved to be handled and could be taken anywhere with me without any sort of harness or cage with no fear of them running off or being lost. As such I am very confident that you will be able to help your beardie achieve the same, as they are a much more sociable species to begin with.
Ignore the hissing and biting. If the lizard snaps at you, withdraw so you don't get bitten (if they get their side teeth on you it can hurt) but do not back away. Continue with your efforts to pick the dragon up without being bitten and without doing anything aggressive or frightening to the dragon such as grabbing it roughly from above. If you must take it out of its cage during the training process I describe below, before you reach that step in the process -- such as if you have to clean its tank -- do your best to come in sideways with your hand or from the front, with your hand flat, and slide your hand under the dragon's belly before lifting. Make sure that all four feet are supported or it will flail and possibly claw you (this is true of even tamest dragon BTW! They can't help it, they have a powerful need to be in balance and any sense that they are out of balance triggers the flail reflex.) Curl your fingers around it gently but firmly BEFORE lifting, then lift SLOWLY. Place it in some kind of temporary container, then do whatever you need to do and put it back in its cage with the same method. Then leave it alone. It's better to not to this and to instead follow the program carefully but I know it's unavoidable at times -- they'll poo in their cage and it'll have to be cleaned, or whatnot. But for the most part, do your best not to take it out before you reach that point in the program.
Now, here is the "program" I am referring to above. It is a slow, careful step-by-step staging process whereby you teach the reptile not to fear your hand. It is very slow and gradual, perhaps more than necessary for beardies as I developed it for much more wild reptiles, but given how especially and unusually fearful yours appears to be, this may be of some help. (It is also possible that you are seeing some beardie puberty behavior and that it may simply outgrow most of this, making this desensitization program unnecessary, but someone with more expertise on beardies and when they go through puberty would have to comment on that one.)
If the dragon is running away from you, either get it in a corner where it can't run and then do the front or sideways flat-hand slide, or else use your other hand to sort of box it in and discourage it from running in any direction except toward your flat hand. (This one works VERY well with the wild lizards -- the flat hand looks much less scary than the active, moving hand, and given no other option they will always choose to run onto the flat hand rather than confront the moving hand. If the flat hand then does nothing to frighten them, that reinforces the association of a flat, still hand as being something safe.)
Once you succeed on getting the dragon onto your hand without it running away instantly, do NOTHING at first! Just let the dragon sit there on your still, unmoving, flat hand. This is what I mentioned before -- reinforcing the idea that your hand, held still and flat, is a safe place where nothing scary will happen. If the dragon eventually moves off your hand, allow this. You have made progress. Allowing it to leave will further reinforce the message that your flat hand is a safe thing. Do this once or twice a day. The advice the other poster mentioned about putting a shirt that smells like you in the tank at all times is also a very good one. At first, your smell is strange and scary to them, that of a gigantic predator, but if you put one of your shirts in there which you have worn for a day and which smells like you, the smell of you will become a normal, familiar part of their day-to-day life, so when you appear smelling like you do, it won't be a sudden alarming change but rather an extension of something already familiar in its environment. This alone helps reduce a lot of the terror they feel about us.
Also try to be within view of the dragon a lot even when you are not handling it. Place its tank somewhere in the house that is used frequently, so that it has amble opportunity to witness humans going about their business without harassing it. Make a point of looking at the dragon in its tank as you walk by, meeting its eyes and making sure it knows you see it, but without doing ANYTHING else -- just walk away. If we were predators, we would come and try to get it every chance we have -- showing the dragon clearly that we do not do this is another way to help it get over the idea that we are predators and that when we reach for them we are intending to eat them. If it knows that we ignore it most of the time, it will be less likely to assume that we intend to eat it when we do pay attention to it because our behavior pattern has been inconsistent with that of a predator, which they are instinctively programmed to recognize. Since, by acting the way I described, you won't seem to fit that internal programming very well, it will no longer be so primed to react to us using that programming (that is, the run-hide-fight-defend-myself routine.) During the whole taming process you should leave one shirt at a time in the cage (but rotate the shirts to make sure the scent on the shirt doesn't wear off over time, but instead remains fresh and strongly akin to the one you have on your actual body.)
Of course, we will always be huge and looming to them and that can't be avoided, but what can be done is to teach them that huge, looming creatures are not universally dangerous, starting with the flat hand = safe exercise described above. Do that for about a week. Do NOT try to grasp or remove the dragon from the cage during that week, or you will undo the good work you have done. Allow no one else to do these things either. This is a process and you will have to be patient. (Of course, beardies, unlike wild lizards, do tend to want and need attention and out-of-tank time by nature rather than by learning, so if you notice your dragon glassdancing after a couple of days of not being taken out, you may try gently grasping it after getting it onto your hand. If it doesn't panic and begin trying to escape, then it is probably ready to move ahead in the program and you can skip ahead to the lifting section. Glassdancing means it wants out, and it may be much more willing to learn how safe you are by that point! If it does panic when you grasp it, release it immediately. It is not ready to be lifted out yet. But you may still want to skip ahead to the grasping training rather than continuing with the flat-hand desensitization, as you don't want to add more stress by leaving it in there bored for too long. It'll be a balancing act and you'll have to use your best judgment as to when your dragon is ready to move ahead to the next step in this "program".)
Once you feel your dragon is ready, whether because it no longer runs from your flat hand but rather sits on you for a bit and then leaves in a calm manner, or because it has been glassdancing but reacted badly to being grasped, you can start getting it accustomed to being grasped gently. The lifting doesn't come until AFTER you do this stage because the initial lifting will be scary and you will need to grasp it so it doesn't shoot out of your hand and potentially fall and hurt itself. If you have already taught it that being gently grasped is not dangerous, then the lifting stage will be much less scary. So start with the grasping before the lifting. (Since you are dealing with a beardie and not a wild lizard, this step may come sooner than a week, but I am being conservative. Use your best judgment as to when your dragon is ready to move to each next step in this process as I said before.)
Get your dragon on the flat of your hand, just like always. By this point you should be able to slide your flat, palm-up hand under it from the front or side in a normal way without needing to herd it with your other hand, or, if you do need to use your other hand, it doesn't bolt off your flat hand the moment that the moving hand goes away. (If it does leave immediately, but in a calm manner, you may still choose to begin the grasping training, depending on your judgment, but instant running means it needs more time with just the flat hand.) Once you have the dragon in your palm, begin to SLOWLY, GENTLY curl your fingers around its body. Make sure all four feet are on your palm before you do this. If the dragon does not react in any noticeable way to being grasped, congratulations! It has lost most of its fear of your hand in and of itself. This is a major step! You can proceed directly to lifting desensitization.
If, however, the dragon reacts to your fingers closing with any sign of fear or aggression, then open your fingers immediately, but DO NOT withdraw your hand! Just go back to the flat, safe posture. What to do next depends on the lizard's reaction to the return to the flat hand. If it doesn't run, but stays on you once you go flat again, this is good. You probably just closed a bit too quickly or firmly the first time. Try waiting a few seconds, and then grasping again, going more slowly and gently this time. Repeat until you can close your fingers around the lizard without it exhibiting any noticeable reaction to the grasping (such as wiggling, gaping, trying to bite, flailing, hissing, bearding, blackening, pulling against your grip, etc.) If it pulls against your grip but then relaxes, that's all right. It had a momentary fear reaction but then relaxed.
If it allowed you to grip it without fear from the first attempt then you are probably safe to try lifting it immediately. If it took a few tries, however, before you achieved comfort, then you should continue with the grasping step for another day or two at least. After grasping it for a few seconds without it reacting, open your hand again and give it the chance to leave you. You can either wait for it to leave on its own, or gently slide it off your hand and leave it. Either one is good and they communicate the same thing, more or less. Do the same routine again later the same day, or the next day, until you can get it to accept being grasped without any apparent fear reaction on the first try. At that point it is ready to move on to the lifting stage.
On the day you are going to begin the lifting stage, first briefly recapitulate the earlier two stages. Get the lizard onto your hand, preferably without using the other hand to herd it there (that shouldn't still be needed at this point given you are working with a beardie). Then briefly, gently grasp it without lifting it. After a few moments, though, instead of opening your hand and letting it go as you usually would, begin to very slowly lift your hand out of the tank. If it begins to struggle, lower your hand to ground level again. If it's still struggling with you at ground level, let it go, wait a few minutes, then try again. This is where the gentle persistence part begins to really come into play. You don't want to back off at this point because that will teach it that it can get out of being taken out of the cage by wiggling or protesting. You want it to learn that being taken out of the cage is not a bad thing at all, but rather a good thing. As such, give it a few minutes to relax again, but then repeat the above actions until you succeed in getting it to allow you to lift it all the way out of its cage without struggling. Once it is out of the cage, but over the open lid, you may open your hand cautiously. If it begins to shoot out of your palm, close your hand quickly, gently but firmly so it doesn't escape, and bring it closer to your body so it can smell you better. (This will help reassure it if you have been doing the shirt in the cage trick.)
At this point it becomes sort of a wash rinse repeat. Take it out as often as possible, holding it in your gently but firmly closed hand, and talk to it. Pet its head. At this point it is unlikely to still hiss or try to bite you when you attempt to pet it, but if it does, don't allow yourself to be bitten, but don't put it down, either. You must communicate absolutely NO fear of its bite to the lizard or it will know it can control you using its bite. Remember to never grip it with any more strength or firmness than absolutely necessary. This will sometimes mean that you are hardly gripping it at all, that your fingers are just resting over its back, and other times it will mean a relatively strong, but still gentle, grasp, so that it can't wiggle out of your hand while it's high off the ground and fall.
You might, at this stage, want to take it to a room like the bathroom where you can provide a controlled, safe environment. Close the doors, then actually put it on the floor and allow it to explore near you. These are bonding experiences for you and the dragon. In the new, strange environment of the room, you will be the most familiar thing present, which by default will help you seem a lot safer. When it begins to go too far from you or go somewhere you feel it shouldn't, simply slide your hand under its belly and slowly lift it just like usual, return it to a more appropriate place, but then back off and allow it to explore some more. This gets it used to the idea of being handled frequently by you while still keeping it from feeling excessively confined or trapped by you. With luck it should see you as the most familiar and therefore safest presence in this new place. If it seems to just be running away from you and trying to hide instead of actually exploring in a calm, interested manner, then it probably is not ready for this stage yet. In this case, instead of proceeding directly to interaction when you get to the point that it will let you take it out without wiggling in your grasp or otherwise showing fear, you should use an intermediary stage where, for a few days, you go to the cage, get it on your hand, grasp it, lift it for a few moments, but then lower it and put it back without actually keeping it out or doing anything with it. Most dragons probably won't require this much caution and slowness, but just in case yours does I decided to include mention of this step.
Once you get to the point where you can pick up the lizard, carry it to another room, allow it to explore, and gently redirect its exploration, without the lizard showing any signs of fear at any point in the process -- congratulations! You have tamed the lizard.
At this point you can begin slowly introducing it to the specific things you would like to do with it, such as carrying it on your shirt or shoulder, petting it while it sits in your hand, and so forth. With wild lizards these things are slower and take longer but you should have little trouble with a beardie by this stage. If you are still having problems, feel free to repost here and we will all do our best to help.
With wild lizards I use a somewhat more aggressive approach, with longer times at each stage before moving to the next step, as they are not as inherently gentle-natured as a dragon is but I am modifying this advice based upon my knowledge of dragons and their typical temperaments and ways. With that said I have never actually had to tame a reluctant dragon, as I mentioned in the beginning, so you should definitely also wait to see what others with direct experience taming beardies have to say. I hope some of this proves helpful, though! Good luck!
