I did a really fun trip on the Upper Green Gorge last Saturday, my first time down (thank you Claire Hews, for leading the way and showing me a clean line through Mercury!) Afterwards Claire pointed me towards this nice instructional video from the Nantahala Outdoor Center on how to execute a good water boof, it’s a good article and the video has explanations that pop up as people boof in slow motion, so it’s really easy to see the different steps.
Update: After I posted this Claire told me that not only is this the video that taught her the boof, but when she does this boof now the song from the video actually plays in her head. Too funny. :)
Update 2011: Unfortunately that cool video on the NOC site is no longer working, but the post is still there and worth reading. In the meantime I’ve posted some more good boofing videos on this site.