Be Yourself - Start with your own personal style. Think about the clothing styles you currently have and the stores where you normally shop. Wearing clothes that look good on you will ensure meaningful photographs that are true reflections of who you are as individuals.
Location, location, location. Consider the setting of where your shoot will take place. Will it be at the park, downtown, your home, or somewhere else? Imagine your setting and the types of colors that will be there. Since the setting will end up being the background of your photos, it has a big impact on your overall look. For example, if you plan to have the shoot at a garden, wearing formal outfits might not be the best idea because you would blend in and get lost in the busy background. Ideally, you want to match the background, but not match so much that you become the background.
Colors - A good rule of thumb is to pick out two colors that would go with the location. Typically, pastels (think peach, mint, or lavender) go well with natural scenes. Primary colors such as blue, red, and yellow match modern locations like the city.
Solids & Prints - Our eyes are naturally drawn to patterns, so dressing your kids in prints will help them to stand out. Playful prints such as stripes and polka dots look great on kids. Dress the adults in complementary solids to balance the look. Shy away from logo and word graphics as well as very tight patterns.
Layering - Depending on the season, consider layering your outfits with accessories such as bowties, headbands, rain boots, scarves, jackets, and hats. Accessories add variety to your shots and can also double as fun props!