1. A Good Setup, A Good Balance, A Good Swing
A good tip for improving your golf swing would be improving your setup. A lot of golfers do not have a good balance because they started off from a bad setup. If you have a good and solid setup, you would be able to keep balanced as you swing. Maintaining your balance would give you a solid swing plane as well as a good pivot. Make sure keep your whole body under control during your setup so you could improve your balance and swing.
2. Swinging Too Hard
Although having great distance is essential, having perfect control of your swing is equally important. What usually happens is since you want distance, you give your all you can when you swing. This causes you to wheel around and lose your balance, as you swing too hard. What you would need to do is trust your club. It is already designed to send the ball to great lengths so you would need to focus on making your swing as solid, as steady and as balanced as possible to stay in the fairway.