Be aware of the sensei that teaches the class, watch him over a lot of lessons, listen to how he talks to his students thats the only way for me. I am at a very good school that has a good system. I walked out of one dojo, the sensei was showing his students shuto uke(knife hand block),and the poor lad had a habbit of sticking his thum out instead of tucking it away, and his senseis reply to him was put it away or i will snap it,i was out of there as quick as a flash