I have a fairly extensive guide for Alistar, but wanted to do a fresh quick and dirty update for everyone trying to play the cow:
This is for a gentle balance between tank/aggressor/team support that a lot of people like to see me running when I join a game:
Masteries:
9/0/21
ability power,cooldown,spell pen for offensive, and max out utility taking exp gain, and improved flash+ghostwalk, movespeed/cooldown/greed etc.
Runes: This is important to this build:
Red - Armor pen - you will hit everything harder, especially nice for tower pushes
blue - clairty
gold - toss up, but i'd say clarity (potentially static armor)
quints - movespeed!
1st - Skill build
lvl 1 - pulverize (q)
lvl 2 - roar (e) if getting harrassed hard (headbutt (w) otherwise)
lvl 3 - whatever you didn't get at lvl 2
lvl 4 - pulverize
lvl 5 - pulverize
lvl 6 - unbreakable will (r)
lvl 7 - pulverize
lvl 8 - roar
R > Q > E > W
As you get good with Ali, you typically only use headbutt for positioning. If you can get a mini stun with it by sending someone into a wall, knock someone away from chasing you, or knock someone back to your carries for a kill, thats what you want it for. Keeping it low keeps the mana cost low for a nice positional move.
Item Build:
Start: Sapphire Crystal + 2hp pots
Slot 1: upgrade to Sheen
Slot 2: Boots
Slot 3: Aegis of the Legion (buy all parts slowly as you make trips back)
Slot 2: Upgrade to Boots of Swiftness (exception is super slowdown/stun teams, in which you want mercury treads)
Slot 4: Stinger (this item gives you a nice bit of attack speed, mana regen and CD reduc, all great!)
Slot 4: Upgrade to Nashor's Tooth (the AP and Cooldown will make you scary now in lategame fights, the regen also helps, pulverize's now nearly 1shot minion waves)
Slot 5: Zeal or Brutalizer - This is a choice between extra movespeed or maxing CD reduction. I typically go for the Brutalizer
Slot 1: Upgrade to Trinity Force if you are still in the game.
This makes you a DPS tank. Alistar does not need much to tank, just his Ult on Cooldown. Getting reduced Cooldown after Aegis improves your effectiveness as a initiator tank in many ways. Try it, you may like it!
To answer a few quick questions before they are asked:
Why Ghost walk instead then Clarity or Exhaust?
Alistar's most important role is initiating, Flash takes a while to recharge, and now with your movespeed build and hopefully swiftness boots, you can make great use out of ghostwalk, offensively or defensively. It is great for getting slightly ahead of someone to headbutt them back to your team, or to catch up to a team mate about to die, and stun their chaser, etc. Not having clarity can sometimes be tough, but building the runes the way I do, and using my spells effenciently has not been an issue for me.
Runes and Masteries:
Why armor pen instead than mag pen reds?
Armor pen will primarily hurt towers and enemies more with sheen proc. attacks. Its also a bit easier to last hit early game with them.
Blue and Gold Clarity runes are just awesome and scale very well. Especially when you are neglecting mana regen until much later.
Movespeed quints just pair well with the item build and focus as a dps initiator.
Why max pulverize?
Creep kills mainly, and to make your initiations vs the enemy team hurt as much as possible.
This build is stupid, I die too fast!?
I think you need to learn how to use your skills to save your hide, and also make sure you are feeding kills to your carry so you get assists, and hitting enemies with sheen proc attacks when you engage after every spell.
Things are going bad! What should I do!
Alternate your item build in game.. Are they caster heavy, and you think your lane is going to be a pain.. Build a Chalice right after Sheen, and get Merc Treads, up roar a bit before maxing out pulv.
Took much DEEEPPPSSS! Make a Thornmail, and stack HP. More then likely, dps heavy teams will get a executioner's calling to deal with you. To counter, buy HP items, and things like Guardian Angel, Frozen Heart. maybe even a quicksilver sash. Warden;s Mail also helps. I still suggest going sheen first to assure you can farm minions when you do have a chance to hit them. Keeping roar low allows you to charge sheen for a relatively low mana cost. (20-40 depending on lvl)
Game changing situational purchases: If you are building your Aegis, try to start with the Ruby Crystal or the MP reduction armor. This allows you to make a choice.. Are you ahead, or are you behind? If you are ahead and can validate the purchase, build a phage instead than a Aegis and complete a Trinity Force Early. If you are behind, perhaps build a Chalice first, then work towards an Aegis to improve your short term survivability and staying power.
My Live Stream:
www.livestream.com/nicosharp <-- Volume NSFW (F-bombs and NC-17 humor)
Other Guides:
Ryze'in above the rest [Guide]:
http://www.leagueoflegends.com/board...428#post681428
The Many Faces of Alistar (Extensive Guide):
http://www.leagueoflegends.com/board...ad.php?t=36784