Coordinate: After you've chosen your colour palette, start with one person's outfit (ideally Mom's), pull out a few colours from mom's outfit and begin adding to the other outfits. Coordinating your outfits allows the colours to flow rather than matching. It and allows the outfits to compliment each other.
If you are planning to have your pictures up in your home (which I hope, it is so nice to enlarge beautiful memories) look at your home décor, what colours will compliment the room.
Accessories are great because they can add different looks, a hat for the little boy in the example. Can easily be removed or added, the denim jacket on mom – easily added or removed.
Limit patterns and no characters/logos – they can be distracting, we want you and your family to be the main focus of the images, not the alligator on your son's shirt. If you really want patterns, 1 person or 2 wearing patterns is ok as oppose to everyone in patterns.
Avoid all white or all black
Textures are nice to add, scarves. Belts etc…
Think about the background..don’t blend: these are fall sessions so there will be a lot of green, red, browns
Classic, is nice. Try not to go with big fashion trends, images are great when timeless. How many of us still have the giant bellbottom photos on our walls (or our parents rather)