Bro, being 17 and in my 3rd relationship for the past 9 months, I'll tell you now, you don't want a girlfriend at your age. Yeah, its fun and exciting at first but after a while, you get tired...and you WILL get tired. Kids around this age don't know what love is. My girlfriend is nothing but the ball and chain. No time for friends, partying, work, nothing. All they will want you to do is buy them expensive things they'll never wear (and throw out when you break up) and have you listen to them nag about their day to day problems you couldn't care less about. Sure you'll go out and have "fun" but for me, I'm the kind of guy that likes to be the life of the party. She isn't. She will want me all to herself no matter where we go. She'll want me to snuggle while my friends are begging me to go and play beer pong with them. It just isn't the same. Yeah, she cares about me and scolds me when I smoke or do something stupid because she cares. But at the same time, I don't want another mother. I'm stuck in this relationship. The last time I tried breaking it with her, she nearly drank herself to death and had to be pumped (She's that crazy).
Point is dude, you're not at the age where you need a girlfriend. You may find someone who shares a common passion but don't go off starting a relationship. It's just not the same. A good ol' fashioned friend is the best answer. Bros first and all that. Find someone you like and be friends. Be happy. Don't go looking for something you think you want and dont need.
BUT
If you REALLY want to try your hand at "love" then find a girl you like. Don't be creepy, scary, or awkward, just be cool. Make conversation, but don't talk about boring crap like the weather, the date, the time, or something completely random. Be confident and be nice. You can choose to go with the cute look or the dangerous one. Personally, my girlfriend likes it when I do one then the other. Become good friends. Talk in class, over texts, and see her at lunch often. After a few weeks of building a friendship, ask her out. If she says yes, you're in business. Take her to the movies, out to dinner, desert, whatever. Don't go over top. Good luck man.