Frankly, when it comes to "cooler" and "sexier", it's far more about having a quiet masculine confidence than about the clothes. Stand up straight (slouching says "I'm insecure"), hold your head up and just say "hi" and smile. If they don't say much back, just smile anyway, nod, and keep going. Be friendly, and easy-going, but not desperate. :-) Other than that, as long as you're not wearing a red nose and clown suit, you should be able to carry off just about anything with a laid-back attitude. -- The key is not to look like you're "trying", no too-quirky outfits -- just quietly BE you. That's what really attracts people (especially girls).