Playing hard to get is very important. You must appeal to her power of seduction. Let her use her sensuality and sexuality to "catch" you. The important thing is that once you know a girl is interested in you, and then you can appeal to her power of seduction by playing hard to get. Don't call her every night. Don't make big sexual moves on her at first. You must appear to be interested, yet still holding back a bit - not quite sure if you want the relationship to go further. Make her feel as though she has to work harder to convince you that you do want the relationship to develop.