I'd love to ('Cause I love doing them)

First off, the planes that seem to do them best are things like Cubs, Bipes, even the Chipmunk does them exceptionally well.

Picture that you're making a left turn to final approach. When the plane has turned about 45 degrees (with another 45 degrees to go before it's lined up with the runway) feed in some opposite (right) rudder.

The plane will stop turning, but will slip or "crab" toward the runway - flying sideways so to speak.

This creates a LOT of drag, so the plane usually slows rapidly and looses altitude quickly. For this reason - and the fact that it can be tricky to recover from - it's a good idea to practice this 2 mistakes high