I usually get asked questions about clothing choices before a photo session, so here are some tips I have compiled, based off a coupla year's experience! Hope these are found to be helpful!
1) Avoid everyone in your group wearing all-white, i.e. white shirts with khaki bottoms. This is pretty popular right now, but I really do not advise this at all. It's more of a fad and can really "date" the picture, not to mention, everyone starts to run together in the photo. I prefer contrast and color!
2) It's possible to match without totally matching. For example, a little girl can wear a green dress with purple polka dots, while Mom wears a purple top and Dad wears a green shirt. It's coordinated, but not too-matchy.
3) Solid colors are best, usually in the mid-tone range. Try to avoid white or black. Try to avoid busy patterns.
4) Accessorizing can be fun. A funky necklace or ring, a hat that shows off your personality, awesome shoes, a pretty parasole, etc. Think originality!
5) Layers. A tank/cami with a cute jacket for her. A t-shirt with a sportcoat for him. The jacket or sportcoat can be removed for some shots to create some different "looks" and some variety in your photos.
6) Casual. If it's something you don't want to get dirty or damaged beyond sewing on a button or repairing a split seam, for example, don't wear it. You might be sitting or kneeling on the ground, including concrete, grass, or dirt.
7) Comfortable shoes. More than likely, we'll be doing some walking to different areas during your session. If you want to wear tall/uncomforable shoes in your pictures, bring some comfortable shoes to do the walking, and carry your other pair of shoes with you.
8) Bring touch-up makeup, a hairbrush, anything you think you'll need to freshen up during the session.
Hope all of these ideas help!