Whatever you do to change your golf swing, you have to understand what it does to the face angle at impact. Here are impact drills to help you hit more solid shots with your irons and woods.
1. Stop at Impact Drill
This is the drill that was used by Johnny Miller who won the U.S Open in 1972 and The Open Championship in 1976. He said that this is the best drill that he knows for improving your golf swing. Here is how you can try his drill. You don't need to hit a ball with this drill.
Swing back to the top using your 7 iron
Start your downswing and stop at impact
You don't need to take a follow through
When you stop at impact, try to 1) close the clubface a bit, 2) open your clubface a bit, 3) make it square at impact on purpose. If you are slicer, try to close your clubface a bit impact when you do this drill. If you hit lots of hooks, try to open your clubface at impact and stop there.
If you can get good at this impact drill, it might become hard to hit a bad shot. There are lots of drills and golf tips out there, but they don't always help your game. When you feel like you don't know which drill or golf tip will help your game, try Johnny Miller's impact drill.
2. Impact Bag
Another good impact drill is to use the impact bag. You can purchase one of those impact bags at the golf shop. When you practice with your impact bag, try to hit the impact bag and stop there. You don't need to take any follow through at all. You just hit the bag and stop there. This drill will teach you to keep your head back at impact. If your head moves forward, you won't be able to put all your power into the bag. If you have an old tire that you don't use anymore in your garage, you can use it as well.
You can put your tire on the ground and try to hit it with your 7 iron. When you strike the tire, try not to hit it hard so that you don't hurt yourself. Instead, you should do it in slow motion and stop as you touch the tire with your 7 iron.
3. Hit it and Stop at Impact
After practicing with your impact for a while, try hitting some balls. As you hit your balls, try to hit the ball and stop as soon as you hit your ball. This is similar to the Johnny Miller's impact drill, but since you actually hit the ball, it is more like a practical-type of drill that you can work on. You won't be able to stop at impact completely, but that's ok. Try to limit your folloe through. This is a good way to prevent you from looking up too early. Especially if you are hitting a weak slice to the right or hitting push-slice, this drill will help you hit a straighter shot.
4. Push Something Heavy
You can also try to push something heavy with your iron. You can try pushing your golf bag using your 7 iron. When you are on the golf course, you can use the tire of the golf cart. Push the tire with the clubface of your 7 iron. This drill will teach you the ideal position of your hands, arms and other parts of your body at impact so that you can put all your power into the ball.
Reference: http://www.golfsamurai.net/golfswing/impact-drills.htm