[webgambit]

The best piece of advice I can give is to stay away from McDojo type places. You know the ones. Usually franchises, instructor's with questionable lineage, 'clubs' that will take you from nothing to black belt for a set fee, etc. One in particular has added several new belts in my lifetime just to keep people longer. Some teach their own version of an art, so what you learn won't transfer if you ever move.

Some forums were already suggested. If you're interested in learning about traditional martial arts I highly recommend http://www.karate-budo.com/. It's a small forum and they don't approve everyone (or, they didn't when I joined; not sure now). But the people there are serious about their martial arts.

Others have mentioned researching the schools. I'd recommend researching the Sensei. Find out who he trained under and research that person as well.

My $.02 worth.