OK, first of all, don't put your picture up on hotornot or something stupid like that.... it is a pointless, insecure action, and won't help you at all. Besides, some people look COMPLETELY different in person than in pictures, so you're never going to know exactly where you stand from that alone. This is also why internet dating is very risky: women put up a really hot pic of themselves but in person they look nothing like that. Multiple pics is a must there.
As far as the abs and glutes (butt) are concerned, those are some of the main muscles you use when having sex, so if you put 2 and 2 together you will see women want someone who can bang their little brains out... all day. Abs are, of course, nearly useless without the shirt off, but if you're athletic and thin and have what I describe below, women will be able to fill the rest of the picture in. More than anything, nothing seems to attract women like the nice "V" shape- broad upper body, narrower waist. Broad shoulders and nice pecs, in addition to a flat stomach (with abs) will give you this shape.... it's all about proportion though. This works in much the same way we men are attracted to women with the "hourglass" shape.
Guys who don't get approached, no matter how hot they are, most likely also don't often go places where they can GET approached. From what I have seen, most girls who DO approach, do it in more social settings like parties and clubs and that kinda thing. If you're walking around Wal-Mart trying to get approached, it ain't gonna happen. The real question here is: Does it really matter if they approach you or not? No. In fact I prefer that I get to do most of the approaching, because I really don't like having to turn girls down. This way, I never have to fu-ck with anyone I don't want to. You will find that most women actually do the first signalling, such as making long EC, smiling at you from across the room, etc. If you accept the invitation, you approach. If not, it is like nothing ever happened. But, as people have already said, it is always the man who is the ultimate initiator. She isn't going to just fu-ck you, YOU have to fu-ck HER.... in every sense of the word.