1. Choose a location with plenty of space.
Look for a large, comfortable living space with distance between the subjects and the background. The more you can separate subject from background, the more you’ll put the focus on the people in your photo.
2. Let Grandpa and Grandma sit down, taking priority front and center.
Allow children to stand around them, with little ones seated on laps or held by other grown-ups. If you can avoid kids sitting cross-legged on the floor in the foreground, you’re off to a good start for a formal portrait. But don’t worry too much about it; if there’s just not enough space for everyone, utilizing foreground floor space is a good way to free some real estate for the rest of the family, and it keeps the kids more comfortable.
3. Casual, natural posing is often more appealing than stiff and formal, though it’s trickier, too.
If you’re working on an informal group shot, where family members aren’t posed symmetrically in a "lineup" format, it works well to think of a big group as several smaller groups. By posing people in multiple groups of two or three per section, composing a large and complicated scene becomes more manageable. The results usually look better, too.
4. For formal portraits, pay special attention to balance.
A group of five adults, for example, may make you consider seating two of them in hard-backed chairs and standing the other three behind. Paying attention to head heights and balancing who sits with who stands for symmetry’s sake will help the formal feel. If your family is just too big and you’re forced to shoot a large group lineup, here’s my favorite height trick: Seat the medium-sized people, stand the short people right behind them, and stand the tall people in back.
5. Use soft lighting to help with shadows.
A flash from the front is almost always harsh. Getting the flash off-camera offers shape and is usually a more interesting and shapely light, but it can create shadows on the faces of the folks in the back row. Split the difference, and try getting the flash off the camera axis and bouncing it off a ceiling or using softening modifiers like umbrellas or softboxes to create more pleasing portrait lighting. It’s okay to use on-camera light, especially if it’s only a subtle fill to fight dark shadows.