eye contact and openly smiling is important. If a girl makes eye contact with you, you should not break it until they break the contact first. Not in a creepy fashion of course hah.
Confidence mate, begin working on yourself as well, trying to be more confident and opening up conversations with strangers. If you look at a girl and then immediately look away once you make eye contact it can show that you are intimidated by her, or just not interested, etc.