One of the best ways to impress a guy is to socialize with everyone, in similar proportions. Girls who are social are attractive to guys, because they create a sense of competition. Cool guys like to prove themselves to girls, and this gives them something to aim for. However, don't be too sexy and reveal who you're after too soon. That way, you can keep the mystery out of it.
You can approach a guy by simply asking him to hang out with you. This will help you understand what he wants, and you can then determine whether a date is possible or not. You can also observe the guy's behavior in groups. The guys who want to date women will ask them out, while cowards will ask you to "hang out" and plan to spend as much time with you as they can on their own.
When you know the guy well, you can ask him to become a member of his fraternity. It can also be a good idea to introduce yourself. Some guys will ask you out for drinks or go to a bar. Some will ask you out for food or drinks, but you'll probably be more envious than anything. If you're a girl, you can approach a guy with a crush who is into men.
If the girl rejects you, don't disappear. This makes you look like you're unsure of yourself. Instead, act like it didn't happen at all, and continue talking to her as if nothing had happened. That way, she will be able to see you're confident and can trust you. In addition, you can approach a girl if she likes you, as long as you don't ask her out to a bar.
If you're a girl who's into cooking, you might consider inviting him over for a cooking class. Your guy friend might enjoy learning about new foods, so you can invite him to join you. Or, you can take him to a local museum or zoo to see how he sees the world. He may also enjoy a cooking class or a martial arts session. Whatever you do, just remember to make the most of it!