How about taking steps and putting in measures so that the girl doesn`t flake on you in the first place?
Legitimate reasons are acceptable. i.e. death in the family, family member in the hospital, car broke down, etc. Sometimes sh!t happens and it derails the date. Enough said about that.
Now, here`s what you do when setting up the date. After the date, time and venue have been set, do what David D advises:
HB: "Ok, see you then".
You: "Now, you`re not going to flake on me are you?"
Most if not all girls would say: "Of course not".
Here`s the clincher:
You: "Good because that would be disrespectful. I haven`t been disrespectful to you and I won`t tolerate you being disrespectful to me. If you flake then that will put our friendship into serious jeopardy".
Then say bye and hangup or walk away, whatever you need to in order to end the conversation.
I have personally used this technique with great success. It tells the girl that you won`t tolerate any flakiness because it`s disrespectful to you as a man and she will respect you as a man.
Secondly, adding in the bit about friendship throws her off and gets her guessing, "What did he mean by friendship? Am I not girlfriend material? I`m going to talk to my girlfriends about this. Blah, blah, blah".
During the date of course, you roll with your own DJ style and run with it.
Just my 2 cents.
Cheers,
Mav