Just be careful what you ask for Beeboy - you might just get it and then some. I hear horror stories about 6th to 8th graders and can't imagine such things, but just stay away from any girls who are mentioned in those horror stories.
Friendship is the most important thing, you'll never love a girl you don't like. if she isn't your best friend, she'll never be the love of your life and the one thing I haven't heard mentioned: with every romance fron your first to your last, there is heartbreak and it is called that because is describes it perfectly, you feel like you are crushed inside and will never heal.
Luckily, we all recover and most often move on. Having not even seen your teens yet, likely you'll have a dozen broken hearts before highschool is over, if you think you are ready for that kind of pain, than go for a girl friend, but if you want to learn how relationships work, then you'll really want a friend or friends who are girls.
By the way, the guy who has girls for friends is the guy most likely to get the best girl in the end - they don't feel the pressure of actual dating, but the fun you have is just the same and believe me makes for you making a better boyfriend later on when it really counts :-D
12 is young and for some reason you believe NOW is the time - we all know what it is called but that conversation you need to bring up with parents and peers. But for now, enjoy learning all about girls and don't fix your mind on one. If it is meant to happen it will, but as mentioned before by others, don't chase them, they will run away - cause many kids your age still play tag in the back oof their minds, not seeking romance. No one is going to tell you different, so date if you must, but respect her no matter what or you will earn a reputation that will follow you the rest of your life.