Unless I am there at the request of the performer(s), I don't wander around taking photos. Even if I am, I position myself so I am not in the way of the audience. In an acoustic gig, if possible I use a camera where the shutter sound can be muted so there is no sound when I take a photo. I don't use flash.

Seems like basic good manners to me.

I'm not keen on people who let their children riot all over the place and make a noise either.