I consider myself to be antisocial, but people always smile around me.
Here are a few tricks
Always smile. No matter the forget what. Don't act like some euphoric idiot, just show people you're happy to be around them, and they will like you more.
Keep an image of yourself in your head. Recognize how you want to be better, and how others look at you.
Examine a girl's mood or feelings before talking to her. If she feels annoyed, do the minimal. Ask for a pencil or something, but side conversations usually don't help. If she feels happy towards others, tell a joke, ask her a question, do your best at not changing her mood though.
And remember, don't be afraid to promote your feelings towards someone else. If they get embarrassed and tell others, so what the forget? You should never be afraid of your emotions, stand up to them.