I recently purchased The Classic Magic of Larry Jennings, which is phenomenal. The author, Mike Maxwell, discusses a really quite effective technique for practicing sleights. I thought I'd share it because I figured it might help a lot of people out. In essence, what he says is that one should never take a sleight and practice 100 times in a row in front of a mirror. What one should do instead is alternate performing the sleight with performing the action that covers the sleight. The example used was the pass. When one practices the pass, he or she should do the pass, then simply make the actions that cover the pass--squaring up the deck, raising it to your fingertips, etc. One should alternate between those 100 times because it will make the pass look cleaner by constantly reminding the performer what the covering action should be. Hope this helps!