I think this is a very helpful comment.

Blood Furnace is an excellent chance for your mage to practice helping the tank with a well-timed Counterspell. If your warrior pulls with a ranged weapon, the casters may just stand in place casting if the tank does not stand out of LoS. The summoning mobs in BF will likely start summoning a minion that will likely aggro on the healer with no tank aggro on it. The mage must be 'johnny-on-the-spot' with a counterspell to stop the summon and cause the mob to start running toward the tank. The DK can Death Grip, but I (a mage) have always been the one to do it in the past.

Other mage notes for instances:
- Be the vending machine that Blizzard made you to be. All mana users get a stack of water. Healers get two stacks.
- Get a sheep focus macro or addon. I use a macro and it's hotkeyed to one of my mouse buttons for easy access. Watch your timers and start re-casting Polymorph when you have 5-6 sec or less on it.
- Do not pull aggro. If you do pull aggro, Ice Block is an 8-sec aggro drop, just make sure the tank is next on the aggro list.
- If you're a frost mage, Cold Snap is the emergency button. Use your cooldowns (Water Elem, Icy Veins) to bring down mobs quickly after tank builds aggro. If things go bad, you can reset CD's with a Cold Snap.

I'm sure I'm forgetting something, but these are just a few things I can recall at the moment. I love 5-mans, have a good time, guys!