For which wheel size you want to learn?
There are two topics with videos for 36ers:
Uni Geezer: 36er Mounting tutorial - Unicycles and Equipment - Unicyclist.com
Tutorial on how to do a rolling mount on a 36" unicycle - Riding Advice - Unicyclist.com
Oh, and of course, one for the giraffe:
Rolling Giraffe Mount Tutorial Teaser!!! - General - Unicyclist.com