One really great way to help you deal with pain is to talk to someone about it. Writing in a journal about your feelings also can help you to sort them out; even if you don't know what to write, just sit down with a pen and paper and start writing whatever is going through your mind.
Try to keep yourself occupied so that you aren't feeling totally alone and broken down. Call up your girlfriends and hang out. Volunteer somewhere to fill in extra time; helping people can leave you with good feelings that may replace some of the hurt or emptiness. Take up an extra curricular activity that you've thought about doing before but didn't have enough time. Just don't sit around and wallow in the bad feelings. It can be hard to imagine now, but time will help heal wounds.
As to how you should act around other guys: Well, it's probably too soon to jump into anything serious right now. You should probably allow yourself time to get used to being broken up before you start another relationship.
Just be yourself around guys, though. Act how you feel is natural. If someone's around that catches your eye and you'd like to get to know him better, then let yourself get to know him better. The main thing is, don't try to replace this ended relationship with another one just to stop the hurt. It doesn't work. Allow yourself time to heal, and just go with the flow.
Things will work out.