What I have learned is never just say anthing to a chick while she is walking by. Like nice shoes or hey red is my favorite color. these statements just don't get their attention 99% of the time , Just stop them with a big smile and ask them a question about whatever or where's this or that . By doing this you will increase your confidence and conversation skills. Believe me it will be more fun too, just say "excuse me can I ask you a question"