By becoming an interesting person women will want to see you again, even if you're doing online thing and never met them, you know you are interesting when they start asking *you* out and making it easy for *you* to ask them out. Them wanting to meet you again is important.
Something else is to learn some specific tips:
Bar girls:
If you makeout heavy, then call them to "make sure they got home". The instinct is to not seem "desperate", but because that's what all men do then you end up seeming typical and boring. She will use this to justify flaking on you as you're "just a typical bar makeout guy" and girls makeout with different guys all the time at bars, it's just something to laugh about with their gfs.
Internet:
If you can Get the address of her house (no easy test for this, have to trust your instincts. Internet chicks are usually seeing lots of guys and have lots of guys wanting to meet them all the time. Often they will have a guy they are seeing regularly who will call or might drop-by and then she will flake on you because she doesn't even know you. Also many women put up online profiles when their current relationship is going down the tubes, but he's still around in the background somewhere.
SO here is what you do, I've field tested this dozens of times:
1. Tell her you want to bring a movie over
2. Get her address
3. Tell her your phone is about to go dead, and you don't have a charger with you.
4. Tell her you are going to get off the phone since it's dying and you're coming over.
Why do I say my phone is about to go dead? Because if I don't and the guy says "Im on my way over" she will panic and flake on me. If she knows I am coming over and she can't get a hold of me to tell me not to, then she is forced to make up some excuse to get rid of him no matter how much he pressures her, least he be there and some other guy show up.
There are lots more examples, but that's a start,