Clipping is not neccessary, but many keepers like to so they don't get so scratched up during handling.
I find that using a substrate of tiles helped to wear down my beardies nails enough so that I don't have to clip them.
If you do decide to clip your beardie's nails, use a human nail clippers. There are lizard nail clippers available at pet stores, but the human kind work much better. The key is to clip just above the quick. As I've never clipped Budo's nails, I can't be of much help identifying the quick, but if you clip past it, it will hurt your beardie and may start to bleed. Clip the very tip of the nails only.