Talk to her. Sounds impressive? Well you rarely will impress a girl favorably by strutting around, or being the loudest guy in the room or setting her desk on fire. The first step is to strike up a conversation with the girl. It can be casual in fact it should be casual at first, however you want this girl to notice you and talking to her is a great way to start to impress her and to make girlfriends.
Be respectful of her interests and thoughts. Listen to what she says, not exclusively because you should have some input in a conversation, but girls are impressed by guys who actually listen to what they like and don't talk about themselves non-stop. The idea here is to exchange ideas, explore common interests and just get to know her. Self absorbed guys tend to end up with self absorbed girls (we hope so anyway) so an equal exchange of ideas is usually a good thing. It impresses the girls or can help make girlfriends.
Be yourself. If ever there was an overworked piece of advice, there it is. On the other side of the coin, one reason it is overworked is because it works! Trying to be someone else leaves you a lot less time to impress girls and make girlfriends. You will probably end up too busy trying to keep your story and persona straight to impress one girl much less make a girlfriend. Honesty impresses girls a lot more often than pretending to be someone you are not.
Be a friend. Ok, not a new concept is it? Well a girlfriend is a girl who is also a friend. If you really like this girl or girls a lot, then be a friend to her. Listen to her when things are not so good with her. Try not to judge. One of the easiest ways to impress girls and make girlfriends is to be a friend when things are not going well. If you are there when she is not as happy as usual or as bouncy or even has a pimple on her nose, then you may well be the guy she looks at for a boyfriend.
- Treat her as an equal. Again it is not exactly the newest concept on earth but it works for most girls. Girls might be different in that they have different hormones and sometimes seem to have strange thought processes, but most are bright and appreciate being treated as equals. Ask her opinion on topics you know she is interested in or has knowledge of. Respect her opinions, though you don't have to necessarily agree. Nothing impresses girls more than being treated as a person with valid opinions and girls who are impressed make girlfriends.