Avoid white like the plague. Don't wear all-white anything. (Unless you're a bride, and then, well, we'll just make it work ;)
Look for textures - ruffles, collars, cardigans, jewelry, hair pieces - anything that provides interest and more depth to a photo.
Start with a piece you love - in my case, it was my son's outfit to the right - and start building around it. The colors in his tie provided me a scheme and I dug through my closets for stuff I already had. I added and subtracted dozens of pieces from this pile on the floor until I ended up with just the right combination. Lay it out, you will see.
Avoid loud prints, unless you want it to be a focus of the photo. Sometimes a loud print is fun - it's just risky, so be careful. Or bring the piece along to use in some photos (like far away ones) and not in up-close ones (loud prints distract from your pretty face :)