Originally Posted by austinpwnz
As a tank, once the fight starts, you should be the hardest on your team to kill, due to HP/Armor/MR/ merc treads/ whatever. That was covered well up above.
Just to clarify--effective tanking doesn't mean you have to take damage for your team. A tank makes sure his team survives. You do this either by soaking the damage for your friend, or by disabling the enemies. I prefer the latter. This is why I pick Blitz and Alistar as my main tanks. Alistar is very self-sustained and has extremely strong lane, while Blitz is pretty good at zoning, a great initiator, but more squishy.
The secret to successful play as Blitz is realize that you have 2 hard CCs (Rocket Grab and Powerfist is a stun and toss up effectively) and a silence (Static Discharge). This gives you 3 ways to interrupt the enemies. Overdrive also allows him to proc phage item really easily, meaning you can peel DPS from your team quicker than most other tanks.
Most people only have 1 combo with their champs. It's always good to pack a few. Headbutt->pulverize->headbutt can have a vastly different effect than Headbutt->TR->retreat->Headbutt, etc. Advance tanking dictates that you stagger your CD effectively, and more importantly know when it is OK to burn your mana. Headbutting the loan DPS leading the pack is perfectly fine. He will be pushed back and lose up to 300HP, while you lose absolutely nothing but mana that you wouldn't have used otherwise. Same as Blitz--if you're stalling for time, go ahead and burn your ult to kill off the minions. This can often stop a push long enough for your friends to join you. Rammus and Blitz have their ult on very short CD, so you can still expect your ult to be up by the time the fight really starts.