Rajon Rondo is one of the craftiest basketball players in the NBA, and because he is so good at selling his fakes and moves he is very good at finishing at the basket over or arround bigger players. The Rondo fake is a good move for when a bigger defender is on your hip and trying to time your shot up to block it. This move is one of the basketball fundamentals for finishing around the basket, and being able to pivot to score in the paint.
Watch this video to learn how to do a Rondo fake and to see a player demonstrate the move the correct way. Once you have seen the video, and learned the move, it will be up to you to master the move and then start using it in a game. When you do the move make sure that you are under control and that you sell the fake, those are the two biggest keys to the move.