Hank Haney's ten minute slice cure. This will help straighten the plane on your swing and keep the ball in play. I know at least two people that practiced this every week for a month and it mostly cured their 20 year slice

First, Practice this at the range once a week, you will be amazed at the difference. Always play or go to the range once a week.

Second, go to a legit golf store like the pga superstore or a course with a fitting center and get clubs fitted to your swing. You will find that you will hit your irons more pure and your driver much straighter. It makes a huge difference.

For example, I regularly hit my 8 degree big Bertha 290 yards and keep it in play with a 44 inch heavy (76 gram, with an additional 4 gram weight in the grip) low spin shaft adjusted to a slight draw. If I take a standard 10.5 driver with a light 57 gram shaft at 45.5 inches off the rack. I'm lucky to hit it 245 yards with a thirty yard fade.