There are a few things that can cause a slice. The more common ones are: You have an outside/inside swing path or leave your club face too open.
Many tips can be found in Golf Magazine or Golf Digest (both way cheaper then private lessons, you can also get complimentary subscriptions as well)
Here are some of the tips that help me when I'm slicing the ball. Imagine the ball as a clock face. You want to hit through the ball (not at it) from 4 o'clock to 10 o'clock. This can help to promote the inside/outside swing path (when wanting to hit a draw). The second is to think of the club face as a baseball bat, if you have the bat open you are going to hit to right field (fade), if you have the bat closed you are going to hit to left field (draw), if you have the bat square then it should go right up the middle.
Try to practice this swing at 30%, then gradually increase your swing speed and swing at 60% and finally 90%.
Hope this helps.