take a small towel onstage with you
warm up (silently!) ten minutes before start time with some runs, scales or the trickiest bits of your set, then tune up
deffo have a pee before starting
make sure you can see your setlist (it's dark up there!)
be careful where you put any (preferably non alcoholic) drinks, they will fall over one day onto your pedalboard.
Dont be nervous (its a team effort and not you on your own)
Just concentrate on being as tight as you can with the drummer, find and lock into the groove, leave any fancy stuff to the guitarist and singer.
Don't make it too obvious when you start ogling the girls (or boys) - then you will make mistakes!
Enjoy, you're being paid to make people happy, how great a job is that?!!