Try this 14 lesson tutorial by Kevin Taylor all about tapping.. The tutorial summary says... "In this tutorial I'll be going through all the techniques involved in two-handed tapping on the guitar.... right from the very basics all the way up to using all the fingers of both hands, hammer-ons, pull-offs, slides and anything else you can think of. Due to the amount of lessons, I've divided it in multiple tutorials. Each part will focus on different tapping techniques."

http://www.guitartricks.com/tutorial.php?input=13