Cloths tells a lot about who we are, I suggest wear something that's comfortable and that you like. If you feel comfortable and confident in a dress, go for it, if you feel more comfortable in jeans and a t-shirt - that's great!
Don't wear anything to revealing or sexy, it can be intimidating. Also, even if you want to dress nice, wear enough cloths to keep you warm, if you are cold, your body language makes you look uninterested and remote.
Also, don't wear high heels shoes that will keep you from doing fun stuff after the meeting like a walk together or play bowling (I know a couple who ended a first date in a bowling alley, they both had fun though the relationship didn't last long).
I think that casual is the best way to go.