At WorshipArts we teach all types of communication between team members. The first, and easiest to learn is signaling. We use a sign-language "B" if the leader wants to go to the bridge.
There are less obvious signals as well. We went to a worship-leading conference last spring and the speaker said he pops one of his feet back so his toe is on the ground. That can signal the next section etc.
At our church the worship leaders usually raise the neck of their guitar to indicate the end of the song.
Another method is simply to use body language. When I'm leading I'll usually look at the drummer and communicate with my eyes what's next. Or I'll start bouncing a little bit to indicate a desired build.
In my opinion though, the best way to communicate is through vocal cues. When you sing the next line before you get there. This not only gets the team on the same page, but it also leads the congregation as well. This is probably the most difficult to learn, as getting the timing correct can be pesky.
If you've been on a worship team, what kind of communication did you experience during the worship set?