A: Similarly to what Levi said, a good way to befriend people is to take part in some activities together. Like going to school for example. But you might think that you've burnt too many bridges there, or something, then go ahead and join some club. Like martial arts, or chess club - something that you think you could like, and is available in your area. You'll find plenty of people with whom you've got at least a degree of similarity(they joined the club too, after all), and topics for sustained conversations shouldn't be hard to find.
B: If you're doing one thing together(club activity, running in your case, attending classes), you can do more. Ask the people you meet there to go out together. A pub might be out of question at your age, but maybe a cinema, a caffe? Or invite them over? A little bit of assertiveness can go a long way here.
Once you're "there", try to enjoy yourself. Some people might be silly, some might be annoying, but since you've taken pains to get yourself acquainted, they must have something pleasant about them, right? Certainly, you could focus on the bad sides, and complain, criticise, and generally be a douche, or you can try and have a good time.
Just sitting there and looking happy will make others like you, which will make them happy, which will make you happy, which surely will lead to a pleasant time together, and encourage further meetings.
C: Well, it's tricky. Not because women are some mysterious and unpredictable kind of creature, but because people in general are different, and can feel differently about those things.
If I were to give any advice on this, I'd say: treat any woman in the group as you would treat a man*.
*Assuming that your idea of this does not consist of making crude sexist jokes, brofisting one another, and egaging in competitive dickwaving.