1. Group the subjects very close together and position the shorter ones in front.
2. Don’t put them back up against a wall. Have them stand out in the open. (You don’t want to see shadows on the wall behind them and this trick will help.)
3. Stand as far away as you can, but zoom the camera in as much as possible. Their combined faces should nearly fill the viewfinder. Otherwise, walk up closer.
4. One caution on standing far away—If your flash won’t reach that far, then you will have to walk up closer.
5. Have the flash attachment at least six inches from the camera lens to avoid red-eye. Otherwise use red-eye reduction mode on your camera. A good flash diffuser would be preferred, like a Sto-fen or a Gary Fong Lightsphere, which I now use. They greatly soften the flash.
6. Always take several pictures, even if you think the picture was good. You may have moved the camera, or someone may have blinked. If it is a group of a half dozen people, try to get at least 4 shots. Tell them ahead of time you will take four pictures and you want every one of the people to look good on every picture. Some people seem to think if they smile on just one picture that is sufficient!
7. Squeeze the shutter release slowly rather than pushing it down. If you can use a tripod or lean your body against a post or wall, you will be steadier.
8. Look at the expressions on their faces. Tell certain individuals, they need to relax and enjoy this picture. They don’t want to look like a deer in the headlights.
9. If there are clashing clothing colors, don’t put those people next to each other.
10. Have the people stand at an angle so their shoulder is halfway toward you. Also, they should be facing toward the center of the picture. That will make them look thinner. A straight on picture makes them look fat.
11. Have people remove glasses to lessen glare. If they refuse, then position their face at an angle so avoid direct reflection back to you.

This is a lot to remember, so I recommend you practice on your family and friends ahead of time.