OK listen very closely cause I'm about to break some knowledge to you.When there's a silent moment while you're chatting up the girl, just end the conversation.Seriously though never ever try to fill the silent gaps between your conversations, it never works and you come out looking desperate. Just keep it casual and only talk about stuff that you both find as common grounds. Then if there's a silent moment that's your signal that it's time to stop talking with her.That way you'll seem like a genuine guy who's options are wide and you won't have to look desperate.Hope this helps. Cheers!