show up early for gigs.
don't bang the lead singer or the guitar player's girl/boy-friend
Don't join a band that includes a guitarist, the guitarists ex girlfriend and that girlfriends present boyfriend.
Don't join a band that includes a guitarist, the guitarists ex girlfriend and same guitarists ex wife. Both exes before band formed.
Both of these from personal experience but I did not join the second band. Same guitarist, same ex girlfriend in both cases ex wife is more recent ex than ex girlfriend.