Look up the following to help keep you from worrying about normal behaviors:
Arm-Waving, Head-Bobbing, Bearding, and Eye-Popping (especially eye-popping, the first
time you see it, it can really freak you out).
Arm-Waving is a submissive behavior that basically means, "Yes I see you and
I know you can see me...please don't eat me"
Head-Bobbing is a dominant behavior that basically means, "Hey you, I'm in charge
around here" (it is also a male mating behavior)
Bearding (swelling of beard and blackening of beard) means all kinds of different
things depending on the rest of thier body language (all the way down to "hmph, I'm bored!")
Eye-Popping is mostly a pre-shed thing from what I understand, but it definately looks freaky.