I did a stint of bouncing after a divorce a long time ago. You generally develop a sense of who might be a problem.

1) Young bucks snorting and trying to look larger than they are almost always are trouble looking for a place to land.
2) Anyone with a chip on their shoulder.
3) Women who like to flirt openly with multiple men.
Take your pick.

In Oregon bartenders are now held accountable for over serving customers.
That has reduced the number of bar fights some.
It doesn't stop serious drunks from loading up before they walk in the door,
but can you do other than spot them early and send them on their way.

Glad I got out of that business.