To me sexy is personality, humor. Things like that. If you have a wonderful personality & a great sense of humor then you defiantly are a sexy person. Don't let the looks or persona of the world and how they feel on looks make your decision. Just be your self to be sexy!
Tricky question. I think girls that are sexy, are just sexy, if you see what I mean. For me, it's nothing to do with what she's wearing, or the perfume she's using. A truly sexy girl will look sexy whether she's in a million dollar dress with immaculate hair and make up, or with no make up, wearing an old potato sack. I guess it comes down to chemistry at the end of the day. My advice would be: If you want to be sexy, then be natural-don't try too hard. I find friendly, natural girls with a sense of humor far sexier than those that are dressed to kill. The knock 'em dead approach may initially attract attention, but it soon loses its appeal.
There are lots of things that make people sexy, but I think the main thing is confidence. Not in a cocky way, but in a "I'm comfortable with who I am" way. If you like who you are then others will gravitate towards that.