Case by case basis. If it's a decent pool hall, and it's huge drunken gorrilla, then I'll bring it to mgmt's attn. If the person looks approachable, then I'm not shy, I'll tell 'em if mgmt isn't on it (without embarrassing 'em).
If it's a super hot babe, I'll just ask her "Whatcha drinking there that's sitting on the rail? Care for another?"
If it's a super hot babe, I'll just ask her "Whatcha drinking there that's sitting on the rail? Care for another?"