If you are playing off of sheet music and you play outside, bring either clamps or use a piece of acrylic to put over your notes or you'll see them fly. alternatively, put them into a ring book with plastic document covers if you don't have to turn pages mid-song.
When doing your own soundcheck use a CD with a song you know and like for doing the PA set up (applies to solo artists like me who only need to adjust master EQ and volume and don't have to care about individual sound ratios).
If you don't have anything better handy, a replacement pick can be tucked between the three top strings between the nut (esp. for floyd users, tuning will not be affected). If you drop one mid-song, just reach up to the headstock and grab it. If you use that one too, pull a crazy tapping lick and pray that the song will be over quick ;-)
In addition to "bring everything for yourself", if you are like me, you have everything twice, especially leads, strings, guitar straps. Been there, done that.
so long
ace