Originally saw this video at ProPhotoLife.com and found it to be very useful. I just need to get a reversing ring to try this out at home. I tried it handheld the other day, but with two zoom lenses, it was a bit of a challenge to get a focus. Definitely be easier with a reversing ring and a tripod (I have the tripod).

extreme macro photography trick from Jim Talkington on Vimeo.