1. It's not behind their backs. It's just not in their immediate vicinity.
2. You are not allowed to criticize your top 25 percent favorite co-workers, except, maybe, if you really really have to, very gently, and rarely, to your spouse or some significant other.
3. You are only allowed to criticize your second favorite 25 percent co-workers (so percentile 50 to 75) when you are talking to your top favorite co-workers. Plus, you must also acknowledge their virtues when you do so. Plus, it can't be trivial, you have to be right.
4. There is a hard cut off each day. When you have complained ten times about your co-workers total you have to stop complaining. Your soul is keeping score!
5. No dancing around the fact of complaining about someone! You can't go around saying "I wonder why there are all these deranged and restrictive notes on patrons' records?" When what you're saying is better expressed by "Louise is inventing policies to avoid helping people again."
6. Never pass along one co-worker's complaint about someone to that actual person. No one ever really wants to know people's complaints against them.
7. The truth is sacred. You must accept someone's legitimate complaint about one of your co-workers, even if that person is pretty much your favorite co-worker. The best you can do is something like "Sure, Sven isn't so hot at the alphabet, but I have never seen a single customer who doesn't adore him."
8. Never complain directly to someone no matter how honest it seems. It never goes well, plus, see title of list.
9. Every once in awhile complain about yourself. It will keep everyone alert and light on their feet.
10. You are seriously not allowed to complain about anyone for anything unless you are clearly, rigorously, and/or obviously not guilty of the same thing! Think once. Think twice. Are you sure?
Okay. Complain away.