In reply to Stuart Williams:
A belay mime? That does sound a bit too lax for my comfort.
My local wall requires you to fill in a form stating you understand about belaying and climbing (standard Mountaineering Scotland participation statement form), then present yourself to the duty instructor who will observe you putting on a harness, tying in, belaying, lowering and catching a fall, whilst they tail the rope. If all is well, you get signed off and can come in unsupervised, if not, you need to be accompanied by a registered climber or take a course.
Fairly stringent but belaying standards are generally fairly high.