There are two types of pace lines. One rotates based upon a schedule and the other is constantly rotating. In the constant rotation, the lead rider takes a couple of pedal strokes and moves right or left and then goes back. The goal of the rotating line is to share the work evenly, It is not the fastest.
With a scheduled line, each rider has a defined time to be in the lead. Stronger riders stay on the front longer. This is the classic team pursuit or team time trial approach.
Since you have 4 riders, it would be pretty easy to determine a schedule. The other fine point is the order of the riders. A less strong rider could be on the wheel of a bigger rider offering more draft.