Personally, I think you should always tell your opponent they are shooting the wrong ball, or shooting in the wrong hole (in One Pocket)...
I feel that if I need for my opponent to shoot the wrong ball and commit a foul just so i can win, then I should probably play better. Its sort of like silently wishing for your opponent to miscue during a routine run-out so you can win. Its lame. I understand that everyone wants to win, and so do I, but there are other ways of going about it.
Others argue its not your job to tell them what to shoot, etc... but on the premise of being a decent individual and not betting my last dollar on a game, I think its the right thing to do. (if you are betting your last dollar, time for a life re-evaluation)
I feel that if I need for my opponent to shoot the wrong ball and commit a foul just so i can win, then I should probably play better. Its sort of like silently wishing for your opponent to miscue during a routine run-out so you can win. Its lame. I understand that everyone wants to win, and so do I, but there are other ways of going about it.
Others argue its not your job to tell them what to shoot, etc... but on the premise of being a decent individual and not betting my last dollar on a game, I think its the right thing to do. (if you are betting your last dollar, time for a life re-evaluation)