To flakes there's always tomorrow:
"I know we made plans and you blocked off your night to hang out with me and it's too late for you to really do anything else, but I'm a little tired. Can we hang out tomorrow?"
No, motherfucker. No. Why am I going to give you another day of my life to waste? If you make firm plans with someone, you should follow the fuck through. I can understand if there's a family emergency or something in that vein, but being "tired" is unacceptable. It reaches the point where you should go out just to be a friend and a non-flake. You piece of shit. If I had my way, flakes would be executed. You don't say please or thank you? Fine. You're an asshole. But to make plans and not follow through, THAT'S the lowest of the low when it comes to shitty manners and I won't put up with it. Flake once and you're done. End of story. Bye.