Here's one Don't that I feel strongly about. NEVER trade within your division UNLESS you are robbing your opponent. I will not trade within my division unless I am getting a steal of a deal.
Reason- Most times you play your divisional opponents twice. You make a bad trade and you lose 2 games. If it's a questionable trade you can always find a deal that is similar somewhere outside of your division. In Fantasy football USUALLY one of the Divisional champs goes on to win the league. Wild Card teams seldom do unless a stroke of huge luck. That makes divisional play even more important. Your Division is the enemy, why do something that your enemy wants to do, that may hurt you.
Again if this is a no- brainer trade (ron dayne for ricky williams)then this rule goes out the window, but if it's not a guaranteed win for you, then I would advise against it.