The two things most 100-shooters need to work on are alignment and tempo. You should never align your body based on where your drives are going, and swinging faster doesn't necessarily mean the ball will go farther. Yet, these are the two most common faults of players who can't break 100. Here are a few tips to help you get into the 90s.
Alignment and Tempo
I first saw this image in Golf Digest when I was growing up, and it's always stayed with me. It really works. Visualize train tracks, pretending you're standing on one rail and your ball is teed up on the other rail. This is a great way to get your alignment straightened out. But remember, your shoulders, hips and feet all have to be aligned with the rail. I work very hard on alignment. It's not something players at any level should take for granted.
The one thing anyone can do is set up to the ball properly. Usually what happens is that amateurs stand too far from the ball. They feel that to hit the ball solidly, they need to reach out to get the arms away from the body. But that creates tension and a weak, armsy swing. Instead, let your arms relax as you hold the driver. Think of how a shortstop or a linebacker stands when getting ready to make a play. The arms hang down, not extended from the body. You are relaxed but athletic.