Listen to what the drummer plays on the hi-hat or the ride. If you've every practiced with a metronome, think of what is played on either of those two as the metronome beats. A crash cymbal is usually hit on the first beat of a measure, especially after a drum roll. If you play in time with the hi-hat/ride, you and the drummer should be in sync. The snare and bass drum are the drummer's own improv. to what he's feeling in the music. Also, a good drummer will mostly likely syncopate these two, so if your following those. You'll have problems. When the drummer does a drum roll just maintain what you've been playing, and let the drummer fall back in time with you.

Whoever wrote or starts the song should take the lead, while everyone else including the drummer follows. When your in the lead, your job is to maintain the song form, while everyone fits to what you do. If the drummer starts the song, the rhythm section should add something first. So just start of with a rhythm guitar part, rather than an overly complex riff. Once you fall into the groove, then start showing what you can do. If someone wants to take a solo, call it it so that everyone knows to just fall back, give that person some room, and keep a strong rhythm backing to whoever leads.

Once you've been playing with a drummer for alittle while, some of the more complex relationships between you and the drummer will take there place. Start with something simple until you get it. Communication is the key, if everyone stays shy and quite nothing will get done.