Link.
Here's a sample:
EDIT: Here's another great post in the same vein.
Here's a sample:
1. Don't yell "MEDIC!" when we're in spawn before the game starts, or during setup - unless you're a soldier or a demoman and actually intend to damage yourself. If you're one of those two classes and don't make use of the healing to build up uber, I'm going to ignore you until the game starts.
2. Don't yell "MEDIC!" on the field unless you A) actually require healing, or B) can see that I have no other targets, and you want to make a push.
3. Don't yell "MEDIC!" AFTER you've grabbed a medipak or healed at a dispenser. Wth, dude? You're fine. Don't distract me from those who aren't.
EDIT: Here's another great post in the same vein.