1) The tank or healer (opposite of whatever I run as) leave in a hurry and I notice the DPS haven't been brain dead the entire run.

2) When I'm tanking the healer doesn't DPS or is just lazy, then it goes to the DPS.

3) When I heal if the tank is single pulling or skittish for any reason. Goes to the DPS.

Basically: Don't be stupid, be decent, and actually try and there's a chance you're going to get a comm from me.