well i dont have any special rules, except for one thing i realy dont like:
when people insist on playing pop songs just because they think its funny
when people dont want to play "your" song so they just make noises in the background instead of turning the amps off

ok thats two things, not one ;)

songs to play

leave my girl alone
crossfire (srv's song)
you shook me all night long - ac/dc
stairway (no stairway?! denied!)
rock'n'roll (led zeppelin's as well)
anything that is 12 bar blues
cold shot
have you ever loved a woman?
blues power
smoke on the water (well its a must )