1) Avoid words, logos or busy patterns on clothing. It's distracting.
2) Skip the sleeveless. No one's arms look fabulous in a sleeveless top. They really don't.
3) Matching. Don't do it. Except maybe twins.. but even then, probably not. Think coordinating. Avoid identical.
4) Fabric that looks aged. If the colors are washed out or it's pilling, leave it at home.
5) Uncomfortable. Question: Who wants to be uncomfortable? Answer: No One. That's who. Choose an outfit you're comfortable in and that makes you feel good. Your images will be better for it.