I think sexy comes down to the two great C's of confidence and competence: knowing you're great and doing what you love well. If you want to be hot just focus on yourself, and take delight in what you find. Cute outfits, makeup, and a great body are all just basically window dressing if you have that thing that makes people notice you and want to know you. From my interactions with you, you already seem to project those qualities. So my best advice would be to just be yourself.
Soundtrack for the concept:
[YOUTUBE="http://www.youtube.com/watch?v=u7aDstrDMf0"]Short skirt, long jacket[/YOUTUBE]