Subtle variation on the confidence thing - Competance.
I like guys who are competant. At whatever it is they happen to be doing. I’ve gone for engineers, dancers, military types, cooks, programmers, carpenters, musicians… the one underlying thing about all of them is that they were good at what they did. They didn’t fake it, they just did it. They dressed for themselves, but they respected themselves too, and it generally showed in how they dressed.
As for who approaches whom, the culture varies by location - some places it is ‘standard’ for the guy to do all the approaching, others it doesn’t matter, others (like local to me) the girls better get off their butts, because guys won’t move without a direct invitation. But most people respond well to an honest approach, even if they thought it was their job to do so.
Speaking as a female who not only approached guys but also did so well before 18, my advice:
A) Be aware of what kind of woman you are looking for. If you are an engineer-type, you’ll find that the women who will like what you have to offer are those who dress appropriately to any situation. That is, they see social situations as events with function, and their clothing fits that function. Women who always dress ‘hot’ regardless of situation are not ones you will appreciate in the long run, nor will they appreciate you. If you’re more of a lawyer type, women who dress conservatively (but comfortably) will find you more appealing. Go look in the back of the Dress for Success books for women - there are interesting notes on what attire appeals to whom, and why. You can often ID the kind of guy they’re looking for by how they dress, strangely enough. Aim for the wrong kind, and you won’t meet their goals - end of progress, because you aren’t offering what they are looking for.
B) Image does count. For those who say ‘my personality is all I need’ - well, the right person can’t see your personality from across a room. You’ve got to have a visible reason for them to want to talk to you. Image won’t keep them there, your personality will. But you’ve got to make contact first. And never underestimate the opinion of the girlfriends’ assessment from across the room. If they say ‘UGH! HIM?’ a lot of women will second-guess themselves, and you lose. Care about how you look, let who you (and that you like who you are) show in your clothes, body, style.
C) Do things you either are good at or want to become good at (and do those until you’re good at them). Enjoy yourself, and lose yourself in whatever the activity is… I’ve gotten that ‘holy COW, look at HIM!’ reaction more often when seeing a guy just doing stuff he’s good at than at any other time. Faking it is helpful, but actually being competant fires up the genes that say ‘make babies with HIM!’ So, you don’t want babies yet, but that is the first step in the ‘getting serious’ process. Fire up the hormones. 
I’ve gotten the same ‘let me have your baby, or at least let me into your pants’ reaction from watching a guy at a PC, working out the hiccups in a computer program, as watching a guy training a dog, as watching a guy playing piano, as watching a guy whip up some wicked jalapeno cornbread, as watching a guy do a perfect (and difficult) dive off the diving board. Doesn’t have to be physical. Just develop things you like doing and become good at them.
That’s all I can think of at the moment. If you develop who you are, like who you are, respect who you are, and let that show, the right girl will notice you, and/or won’t hesitate too much when you notice her.
(And double-ditto on not ‘wanting’ it too much - I can smell that miles away, and it is not appealing. The guys who didn’t think they could get me, or who weren’t even paying attention generally got way more noticed, and less avoided.)
relatively young women out there that happen to be grandmothers.