I think if you know nothing about the martial art, credentials are useful. However I think if you are experienced I would say credentials are a distraction.
Too much focus on credentials inevitably ends with a rigid set of 'things' which the teacher should know, and the martial or teaching ability gets lost.
This is the best way to check someones credentials: attack one of their unsuspecting students; if they give you a good response, I'd guess the teacher is pretty good.
P.S. I trained once with an instructor in London who said he taught 'aikido'. Not only was he quite a violent man, but he had no concept of why what he was doing was not aikido (it was like 2nd rate ju-jitsu), and unfortunately his students followed him blindly.
P.P.S. I always lament that teaching certificates are not given out, so when you kick somone's arse it discredits their lineage!
Last edited by ian : 02-09-2006 at 07:30 AM.