Lucas Leite was a machine at the Mundials (World BJJ Championships) this year. Every time that he got into half guard bottom on anyone, he was sweeping them.
Half Guard Sweep from the BJJ Worlds
The key to this technique is using your underhook to pull your opponent off of his base (watch around :30 second mark) so that you can get up to your knees. Once you are on your knees, you have all of the leverage you need to turn your opponent over.
Also note that this sweep works best when your opponent gets a wizzer (overhook) on your arm. You can clamp your elbow (left elbow in this video) down on his arm to prevent him from basing out as you sweep. If he doesn’t use an overhook, take his back.
Give this sweep a shot. If you are planning on using it nogi, grab under the shin or under the hamstring when you are going for the sweep.