Confidence is one of the sexiest traits in both men and women.
No matter what sex you are, if you carry yourself with confidence, you will appear to be attractive.
You can even be a little bit arrogant.
Women tend to like that.
Try not to be over-confident and do not place your confidence in the wrong things. The number of women who will be impressed by your level 80 World of Warcraft account is very small. If you want to be confident in a certain trait or talent then make sure that it is justifiable.
While being confident, you need to give her the opportunity to talk about herself and ask her questions about her life. If you only talk about yourself, she will feel like you aren't interested in her.