Put your camera in macro(close-up) mode. The symbol for this mode is a little tulip looking flower.
If possible, connect your camera to the TV so as to use your tv as the viewfinder to help with angling and pointing the camera.
Don't get the camera too close.. about 1 foot should be minimum, 1-2 feet max with macro mode. This will allow the camera to focus properly
Using a flash normally produces a clearer picture, but the angling of teeth can sometimes cause glare, I prefer to use a flash still.
Don't be afraid to get more than your teeth in the picture, the more well lit area there is to focus, the clearer the picture. You can crop out your face/nose/chin/horns/whatever later.
I hope this helps some people
