Here's what jumps out at me when I see players yipping chip shots:
The left arm stops dead just before impact, and the right hand flips. If this sounds familiar--you know who you are--the trick is to learn to keep your left arm moving through the shot.
I have a drill that can help. Take your normal setup: stance narrow, ball just behind center, weight favoring the front foot. Then make your regular chipping stroke, except drop your right hand off the grip just before impact. Focus on keeping your left arm swinging to the target (above). With your yipping hand off the club and your lead arm moving through, you physically can't do what yippers do.
The other part of yipping is the fear that you can't control it. To combat that, don't delay. Make two practice swings, dropping your right hand off, then get in there and make your normal stroke. Your swing thought: Keep the left arm moving.
Chunked chips usually come from trying to help the ball up. But you don't need height on a chip shot--you need solid contact. Try this drill: Set a headcover a foot behind the ball and practice chipping without touching the headcover. Play the ball back, lean left, and swing. Miss the headcover, and you'll catch the ball flush.
Butch Harmon operates his golf school at Rio Secco Golf Club in Henderson, Nev.