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In my experience, it works like this:
If you want something short-term, be direct and honest, and don't waste time on girls who don't immediately show interest.
If you want something long-term, you have to slowly build her interest in you over time. She must like you to begin with, but for her interest to grow, she must wonder about you. She must be a little unclear on where she stands with you until she reaches the point where she's ready for a committed relationship. That's why push/pull works, at least if you're looking for something long-term.