Know what to play
1. Know the scales
2. Preparation: Practice, Rehearse, Sound Check, Perform

Listen to each other
Bass - bass guitar; kick drum and floor/ rack toms
Contour - rhythm guitar; keys; vocals
Treble - keys, lead guitar; female vocals

When and when not to play

Understand the song
1. Sometimes, a song does not need the guitar, but, for instance, the keys.
2. Most importantly, the songs represent expression to God; what one plays needs to tie-in with the song's message.