Where would i find the stage door at concert venue?

I've had the best luck waiting for the bus to arrive to the venue and meeting people as they unloaded. Granted, we're talking smaller theaters and clubs. My example is the musician Five For Fighting and his band and crew. They unloaded their trailer behind or next to the venues and they didn't mind me taking photos of their activities. I was able to talk to the techs, the band, even the bus driver...he actually let me on the bus! And, yes, I met John Ondrasik, too! If you want to do this, be prepared to be there about 6 hours before the show.