Well this of course, isn't a universal answer but anyway :P
I like a girl that I don't know very well, I try to approach her, talk to her at parties. Maybe I just happen to show up next to her a bit more then what is considered accidental...If you notice that a guy is concentrating on you, even when you are in a group. And if you see him looking at you from across the room. If it's a girl I know a bit better, I like to give gifts, flowers and chocolate and stuff like that... ^^ Hope this helped.
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