I usually go for something I feel confident in, and yet have a degree of comfortability wearing. You need to seem like you are in control, and sure of yourself, and if you are wearing something that you don't like, it'll show. That being said, I also like to throw a piece of jewelry or a clothing item that definitely represent me, and show that I have a personality.
My go-to outfit is usually a pair of comfortable slacks (Dressy, but ones I also can wear for shows-usually dark grey or black), A dressy dark top of some kind, and simple earrings. I try to not draw too much attention to my upper half, because of my body type (I'm a rather large-chested girl). My statement piece is a brass cuff bracelet with a 1903 map of Detroit etched onto it. It's a good conversation starter, and shows a bit of my personality.
Oh, for ladies, something I have heard often: Please keep the makeup to a minimum. Yes, we want to look good, but the more natural, the better, because it shows that you aren't trying too hard, and are comfortable in your own skin.