Something like this:
An important specification to know for any of your lenses is MFD, or Minimum Focus Distance. The MFD is the absolute closest your subject can be to the focal plane (normally your sensor in a dSLR) while still having the lens able to focus on the subject.
The temptation with an Ultra-Wide is to spin it back to its widest setting, and try to get in as much of the scene as possible. While this is an appropriate technique in some circumstances, it's generally a whole lot more gratifying to use the usually much shorter MFD to take advantage of the inherent distortion in such a lens.
The cat above is quite the butterball, but you'd never know it from the picture. I got down nose-to-nose with her, and shooting at 10mm, got as close I could while still being able to focus. She obliged me (for once) by stretching her neck out to see what I was doing.
Shooting at aperture of f/5.6, to increase DoF (and compensate for any missed focus) I made the shot. If I were using my next-widest lens, which goes as wide as 17mm, I would have had to have pulled the camera back an additional four inches, and it would have looked a more normally-framed shot, and more of the cat's Rubenesque shape would have been apparent.
