It all really depends on your mindset, on what you want. If your mindset is to sleep with lots of girls, chasing one particular girl is a waste of time. You go for one-two dates, you spent with that girl couple of hours, and then you move on...
On the other hand, if you are looking for more stable relationship, giving up after one-two dates is silly. It doesn't make sense. There are lots of great girls who will not sleep with you until X dates, it is just a number in their mind - all you have to do is keep being persistent, resp. keep showing interest without chasing, without being overly obsessed with that girl... You need lots of patience because it is a battle for days and weeks, not just 3-4 hours... You need strong frame, and each time you want to move further then you were last time... As long as there is a progress and she is going out with you, simply keep going, keep doing the same...
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If she goes for a first date but then she doesn't show more interest, she's not responding, she is flaking - she simply didn't find you attractive enough. Move on, chances are high that you are wasting your time on her...
If she goes for couple of dates and there is no progress - you have to check what do you want with her. Most likely you are hanging too close to a friend zone, if you don't make a move you will become a great friend, but not lover... You are missing actions, you are not leading, she likes you but you are too passive...
If she goes for couple of dates and the progress is there - keep going, don't give up. She is interested, but for whatever reason she has a foot on her breaks. It is what it is, just be patient, keep what you are doing, don't try to change your frame much because you want to be congruent. She likes what she's seeing and what you are doing, there is no reason to change your behavior...