The only kind of love I really consider to be "love" is to be so infatuated with someone that you want to share the rest of your life with them. I don't consider lust to be the same thing, nor any love that is bound to any sort of physical conditions. I'm not going to take the scientific route and say it's all about passing on genes, because all anybody who says that is doing is taking a few pages from Freud so they can take a wild stab in the dark. It neither addresses what love actually is nor in any way explains how or why it happens--scientifically, psychologically, or otherwise. I think psychology is very useful in many situations, but any time it tries to approach love it becomes laden with so much bullshit and conjecture anyone should be ashamed to call the approach a science.
I think love can develop quickly or slowly, but I think when making the commitment you should take your time. I feel like people should be in a relationship at least two or three years before getting married, maybe more. They need to be able to have arguments and work things out together. They don't have to agree on everything, but I think a few things like lifestyle, values, and desire for children are some pretty major things that can't easily be ignored. I think people can fall in and out of love--people change, and someone who was right for you can change into another who isn't, and vice versa.
In my experience, the most consistently successful relationships develop from friendships. I feel like starting out as friends you get to know each other quickly and easily without that romantic pressure to impress or hide your flaws. Of course everybody naturally does that around their friends to some degree, but when you like somebody you become even more hypersensitive to it, and try harder than usual to please them. As friends, you go in already knowing quite a bit about each other's characters and interests. It doesn't mean success is guaranteed, but it can make forming the relationship a lot smoother of a transition.
And lastly I don't really agree with the theory of "The One"--or that there is ONE person in the WHOLE WORLD out there for you, and you have to find them. With the sheer number of people in the world, that's just silly. I think a person can grow to a point where they don't want anyone else apart from the one that they have, but I don't feel like that means there can't be another who (if you didn't already feel that way) couldn't do just as well. I personally favor monogamy so I would never actively seek someone else while I'm with my current boyfriend, but if something happened to him or something happened to me I think there could be another out there for either of us. And even if our relationship were more long-term and something like that happened, I don't think I would mind if he pursued someone else. It would be selfish of me to not want him to seek what makes him happy, though I wouldn't mind if he didn't feel like it either.
So those are my musings on love and how it works, take it however you will. I will leave you with this YouTube video, which is a true story of a kind of love I hope I can get even just a piece of someday.