If it's an unknown band, I just stand there and listen. If they're good, I'll throw the horns and headbang a bit. If not, I'll just stand there.
If it's a band I know and love, I scream like a fucking maniac, sing along, throw the horns, headbang, and way every once in a while, I'll go into the pit. Not often at all, though. During Katatonia, I just stood there, headbanged, and sang along (and screamed during 'Murder'). That's probably the tamest band I've seen. During Strapping Young Lad, I just about shredded my voice to nothingness. During Carcass, I went into the pit a bit more, and screamed a lot. During Opeth, I screamed along, sang, headbanged, and went into the pit once. During Blind Guardian, I sang and screamed like there was no tomorrow. Lots of headbanging and horn-throwing, too. Blind Guardian was fuckin' fun. Anyway....