Watch the Tapping online guitar lesson by Angus Clark from Hard Rock Survival Guide: Lead
Tapping yields more quick and easy benefits than sweeping, and that's what I'm demonstrating here. But like sweeping, if you really want to get into it, you can go really deep and make it a hallmark of your style. Players like Eddie Van Halen, Reb Beach, Bumblefoot, and Joel Hoekstra have this the technique wired at a level that I've never even attempted. Check them out if you think it's your kind of thing.