I teach all of mine to sit and then i get behind them and hold their bottom down as they turn their head and then praise them. I also use cheese. They love cheese and i hold it just out of reach and snap away with the camera and say "hold it". when they hold it for 2 seconds, i give them the cheese.
It also helps to have a digital camera and PHOTOSHOP!! LOL!!!
I put my girls up on the kitchen island and then can delete the background out so they look better and you don't see all the junk on my counters! LOL!