I just turned 23 and have only been married for eight months (July '05), but I figured I'd toss in my two cents and concur with what others have said, based on my experience.
-While it's possible to meet "the one" at a bar or club, it's like finding a needle in a haystack. You get lucky every now and then but there are better places to look. I found my wife through my church, which leads me to another point.
-Religion is important. My wife and I go to church together every Sunday and it's a bond that very much strengthens our relationship. I realize that there are others on this board who have very different opinions regarding this, but it's hard for two people to share a life when they have two very different religious views and practices (one goes to church, the other stays home), whether they're Christian, Jew, Muslim, Atheist, etc.
-Your wife must be your best friend. My wife and I were both home for Christmas vacation during college and our relationship actually started with us just hanging out as purely friends, watching movies and stuff. I wasn't expecting it to grow from there like it did, but the more time I spent with her the more I realized I didn't want to be without her. If you find that you'd rather hang out at a bar with the guys than spend the night at home with your wife (and kids, as it later becomes), then maybe this isn't for you.
-When you know, you just know. This isn't very helpful, I know, when you haven't found her, but this isn't an exact science.
-If you're willing to put a little effort into the marriage it definitely gets better over time. Like I said it's only been eight months for us, but the longer you go (and boy, how the time has flown!) the more comfortable you get with one another. Communication is very important. It's scary sometimes being a guy but you have to be willing to go through it when things come up that need to be talked out. Just be honest and respectful and things will work out. This is also means that if you can't talk to her before you get married, then that's not a good sign.