The fish need to be at the surface, or it won't work, and it works better if there are at least a full school of four. If you are lucky enough to find a double school, it's pretty much a given that you'll catch one. In fact, in that case, I've even had a couple jump onto my hook without me having to recast, even when the hook landed without hitting a fish!
Here are a few pictures (NOT of one jumping on, but of good snags). It takes a while to get your aim right, because the water affects the casts differently than if you're casting at something in the air (give phantoms a try...yup) or on the land (anything you like).
