First off, I want you to be comfortable. It's really hard to look comfortable in a picture when you feel uncomfortable. :) Here are some tips to help you coordinate, feel comfortable and look classy as well.
1) Matchy - matchy is a style that has long passed. No two outfit choices should be the same. Usually you can find what you need in your own closet.
2) Try some color combos. These color combos usually make for some great pictures.
Brown and Turquoise
Beige and Red
Brown and Orange
Grey and Yellow
Black and Red
Grey and Purple
3) Layers do wonders. Whether it's layering a cardigan over a cami, a scarf, or even a bulky necklace. For guys it could be a blazer over a plain shirt or sweater, or a plain shirt under a button up shirt.
4) Avoid wearing white. A little white is ok, but too much white will wash out your faces. Try going for the neutral colors of white, like beige or tan.
5) Let's look classy. Avoid wearing something that will show your bra straps. Showing bra straps is not classy in photos (to me). It puts a photographer in an awkward position of "do I say something?" or " should I photoshop the bra strap out of all these pictures?". You see? Another thing is to avoid wearing graphic tees (or at least large graphics). It takes away from the photo because you are drawn to the shirt. And plus, that popular brand you are wearing, might not be so popular later and will date your photos when you look at them 10 years down the road.
6) Shoes can make or break a picture. Try to avoid wearing white shoes and/or socks. The attention will go right to your feet. Gals, high heels can do a lot for a girl in a picture. It makes your legs look slender and makes you stand up straighter.
There are a few tips for what to wear and what not to wear. :) Hope this helps make your outfit decisions easier!