Preparation
One of the main keys to great group photos is preparation. While the size of your group will no doubt determine the location used, scout out several possible spots in advance. Keep in mind that large groups may require established settings, such as bleachers or stairs, to ensure the visibility of all, while smaller groups will photograph better in informal settings, such as around a picnic table. Be sure that all camera batteries are charged and that a separate flash is available to fill in any shadows. Remind all subjects of the location and time of the shoot; then be sure that you are there and ready at the designated time, as well.
Posing
Once everyone has arrived, pose them as quickly as possible. Avoid exact rows if you can. One way to do this is to break a large group into smaller groups, forming each group into a triangular shape, then moving the smaller triangular shapes together. Place taller people toward the back and center and shorter people on the edges of the group. If the occasion focuses on a particular person or couple, then put those in the center. Do not make the group any deeper than necessary so that everyone is in focus. Be sure that there are no distractions in the background, such as a tree growing out of someone's head. Have your subjects turn somewhat toward the side or center and look up slightly for the best shots.
Taking the Photo
Once your subjects are posed, get in as close as you can without cutting off someone's head. Ask everyone to look at the camera. Since there is always the possibility that at least one member of the group will have his eyes shut, be prepared to take several photos. Using a continuous shooting mode can help overcome this problem. While you need to have sufficient light to take the photo, be careful of outdoor shots where the sun is right behind you if you want your subjects not to squint. If any of your subjects are wearing glasses, make sure that there is no glare.
Finishing Touches
View the photo after each shot if possible to make sure everyone is in focus. If the group is smaller ask everyone to wear clothing with matching or complementary colors to unify your photo. Try taking the photo from a different angle for variety. Add a prop such as a chair, trophy or pet for people to gather around. Take the photos as quickly as possible, especially if the subjects are very young because they will not hold still for long.