Just gotta be you man. Don't try to be someone you're not. Relationships are
interesting to say the least. All you can do is ask someone if they fancy you like you fancy them. If you get rejected, yeah, it hurts, but don't give up. One day you'll find someone who is just right for you. Let love find you. You'll know it when it hits you.
So you want to minimize friend troubles? Well, just for advice, don't ask, in your group of friends, one girl out over another. That calls for unwanted bitchyness and could split the group up.
You could find her at school, though I wouldn't recommend it. You don't need other people trying to tell you what the relationship is or isn't at school. People at school will make the relationship what they want it to be, not what you want it to be. You have to put yourself out there if you want to find someone.
For the how and were, just ask right in front of her. You could pull her aside and do it privately, which helps, but you could literally ask her anywhere anytime when you are with her. It's best if you develop a friendly relationship with each other before you rush into a loving relationship. Be honest about your feelings and hope that she feels the same way.