The most important rule in choosing what to wear is that it reflects YOUR style. Don’t wear something you would never, ever wear any other time. Color is your friend! White and black tend to wash people out in photos so I recommend avoiding those (especially white, which not only washes people out but also doesn't generally photograph well; shades of tan or off-white can work better). Your shoes WILL show in some of your photos so don't forget to think about those, too! In the summer, feel free to do your photos barefoot if it makes sense.
For family and group photos, consider choosing one or two coordinating colors and have everyone work around that. For example, shades of blue, green, brown, red, purple, grey and pink photograph well. Busy patterns are best avoided, but it looks nice to have one or two people wear a simple pattern (such as stripes or small floral pattern) and then have the others go with a solid option that matches.
Don't be afraid to incorporate some bold colors in your clothing or bring in additional color with accessories such as scarves, hats, jackets, jewelry or shoes.
Unique, playful yet timeless outfits will make your photos extra special.