it's kinda hard to know for sure if you need to take the guitar down to bare wood, but I will say usually that's the procedure for me. I need to know more of what you are working with, whats the condition of the finish, and what do you want refinish it with. i.e. a poly, urethane, or nitro finish? do you want a solid color, translucent color, metallic, or a burst? etc, etc.
just about everything I've learned about guitar refinishing, I've learned from reranch, it's an AWESOME web site. other then that the key to good finishing is tons of practice, and even more patience.
...and an occasional tip from Danny doesn't hurt either
