The two most common faults I see amateurs make are: not taking enough club into the green and using too much loft around the green. They're both ego mistakes. Everybody wants to hit the ball farther, and everybody loves that soft little pitch shot that nuzzles up to the pin. But reality has to trump your wish list.
Here's my advice: Take an extra club on approach shots, and then swing within yourself. You'll hit the ball solid a lot more often if you go at 75 percent instead of 100. Trust me, your swing will be mechanically better at a speed you can support.
Around the greens, use different clubs—don't just grab your lob wedge. Let the lie and the amount of green you have to work with dictate the club you pick. Then you can use the same swing for most greenside shots. In other words, you're changing clubs, not your swing, to hit different shots. It's simpler that way.
Even when they're pitching with a wedge, most golfers try to help the ball up with a flip of the hands. This is a killer, because it drops the swing's low point behind the ball and leads to chunks and skulls. Here's a good rule: Return the loft. Whatever clubface loft you start with at address, return that loft at impact. To do it, keep your hands leading the clubhead and turn through the shot.
Butch Harmon is a Golf Digest Teaching Professional.