Roosh provides you young boys with some valuable advice about dealing with a girl when she flakes out or stands you up.
I called it 505025, but the lesson is the same - always have stuff to do, and NEVER assume you're going out.
Girls flaking had gotten so bad at one point, and I so accustomed to it, I had forgotten I had a date one time because I just assumed she was going to flake. I was at the bar with some friends when I received the call.
Regardless, you always assume the girl is going to flake. Matter of fact, you may want to flake on the girl and cancel at the last minute. That technique is one of the few that has ALWAYS worked for me (meaning the girl was sure to go out with me when I "rescheduled" the date).