On the day of the date, you want to shoot her a text, preferably early in the day and long before you’re going to meet up. This ensures you that it’s still on and tells her that you’re still in. She’s most likely doing the same thing that you are: waiting for that text so that you both know for sure that you’re both still in and not going to flake. By doing this, you almost guarantee a no-flake scenario between the two of you.
But as this is the point where she did not get back to you and you decided to call (good decision, he gets a courage point). So what about this: Come up (instead of saying that you have been so busy) with a plan. (Think of the mammoth theory) – We LOVE men with plans. You could suggest to do some cool cultural or sportive or whatever thing, maybe you say you have tickets for something and would love to go with her. I think you make yourself more interesting like this. Theater, a cool party, indoor-climbing, black light Mini-Golf…whatever. (If you have talked to her you might have understood if she is sportive or culturally interested.) Generally girls don’t want to date “idiots” (whatever this means as a definition) so if you suggest to go to a museum (there are cool museums as well) or to some event like a vernissage or photographic exhibition she might think: “Uh, he has interesting hobbies and he wants to share this with me" (on top you will have this unforgettable first date and lots of stuff to talk about automatically – just don’t play paintball with her or other aggressive stuff – and if you do at least don’t laugh if you hit her).