He's Perfect

He wants to move in after a few dates, has all the time in the world for you, and after a few weeks begins naming the kids you'll have together. Check his job status; chances are he can't afford his own place. Unless you have aspirations of being a Makeover and/or Sugar Mamma, keep your keys and change your phone number. 
 
Mr. Stand-Up

He shows up late, doesn't call when he says he will, or stands you up entirely. This egotistical specimen is testing to see how much bad behavior you will tolerate. Let him take his bad behavior elsewhere; you've had your fill. 

He's Married, Dating or Living with Someone

If you need an explanation here, there's no hope. Just remember this: what comes around, goes around...
 
The Retro-Date

An ex you agree to go out with because you remember him as being a lot better than he really is. Avoid the embarrassment of explaining to your friends how 'things are different' and then coming to the re-realization that yes, he really was that bad.