Here is a typical lap of a "Follow the Leader" session, which is required of all NEW RIDERS.

Notice the white Xs, which guide the riders onto the proper "line".

The goal is to allow each rider to follow closely behind an instructor and pick up reference points that they can use later during open sessions.  During these sessions, you want to maintain a fairly tight formation, and don't stray from the path of the rider in front of you. 

You'll notice that some riders are more successful at getting the most out of follow the leader than others  :-)