(Image from Worth 1000)Note: This article is written for men, but women are free to read it and critique it for accuracy sake.
Women Theory 101 - The more you demonstrate that you've got your life together the more they love you for it. Everything's a gamble though, there is a tradeoff between how perfect your life is and how much they can offer to keep you in a relationship with them. The key trump card move they can make is to have a baby which might trap you into a permanent relationship, so be careful to use some form of birth control unless you are planning on having a kid or two, but frequent sex only happens if you don't make them feel very important in other regards while they're still trying to keep you. Too much sex in a relationship might make you look bad if you aren't a very good lover, they might get bored and lose interest if they don't have anything else on their relationship agenda to do, so a goal is to not be too perfect for them which you are probably not going to be able to do because they will attempt to start trouble in order to solve trouble if it comes down to that (one avenue for this disfunction is religion). On the other hand, there will be less sex in the relationship if you make them fix too much of your shit in life, and possibly they might leave for somebody less demanding unless you show some amount of forward progress in the relationship.
Am I missing something? Physical attractiveness helps, but that too is included in the aspect of having your life together, maybe lift some weights or do some aerobic exercises and such, the ability to lift a few bags of quickcrete over your head and carry it a reasonable distance can easily make up for having a smaller jousting rod in the bedroom.
