1. Listen to your gut: If something about him doesn't feel right, it probably isn't. Don't let the idea of who you want him to be overshadow that little voice in your head telling you he ain't shit.
2. When it seems too good to be true, too soon, it probably is: I believe there is such a thing as love at first sight, but more often than not this is good game. If he is doing everything that you probably told him that you want in a man right away, be weary. He's had enough practice to be convincing enough to get by for a little while, but time will show you his true colors, and it usually doesn't take too long, especially if he isn't getting what he really wants out of the deal.
3. If he doesn't give you his time: If he's always too busy to take you out but he can find a way to "come through" on the late night, he's probably a fuckboy, pun intended. Or if he never makes time to see you period, he is just using you as something to help pass the time when he gets bored.
4. If he doesn't bring anything to the table: If he doesn't have a job, if he's not in school, or if he isn't doing ANYTHING to better himself or work towards his goals, run. You don't want to be sitting at the table with him. He doesn't have to be a finished product, it's okay if he is a work in progress, but the key words here are WORK and PROGRESS.
5. If he's a mama's/daddy's boy: The last thing you want is a "grown man" who is incapable of doing anything for himself. If he has never paid a bill, worked a job, or made his own doctor's appointment, stay far away. Who wants a grown child, where's the fun in that?