Typically in Lunge Line classes (well, for APHA) the horse is required to circle the demonstrator on a line, through its natural gates, one at a time. Then the horse is brought to a stop, turned around and run through each of the gates again.
With the APHA gates, you have a circle of a walk, then followed by a trot and then a canter. Once each of the gates have been demonstrated, the horse is stopped (facing in upon stop demonstrates attention, not required but plays out nicely), then circled the other direction through them. Equipment we usually use are the show halter, a lead line (cloth or leather matching) and a crop or whip. With the crop or whip, the idea is to not strike the horse but drive. Striking can make some judges view the demonstration negatively. You can gives commands by either voice, noise or any signal that you have trained yours to do.
Judges look for moving confirmation, ease of transition between gates, and confidence of both horse and demonstrator.
Dixon's Red Hot Ember