This guide is intended to go down the list of all heroes and give new players an idea of what those heroes can do. This is not intended for high level play, but rather as a guide for someone who is unfamiliar with an opposing champion to know what those heroes are capable of. I'm pretty expert at dying, so I guess that's my qualification.
A secondary goal is that this guide will be polished/correct to the point where it is useful for all newbs when the game goes full retail.
Perhaps during the loading screen, you could have this open in the background and get to know your enemy - if it worked for Sun Tzu, it will work for you.
I am nowhere near good/experienced enough to write this guide myself, so any contributions and outright contradictions are appreciated. The main posts will be edited and proper attribution given.
Alistar (Minotaur)
Excels at pushing lanes. Can even push towers fairly early in the game. High Hit Points. Low damage.
In Lane - His skills can help his teammates kill, but can have trouble killing 1v1. Don't try too hard to harass him unless you can do lots of damage quickly, he will heal it all over time with his third ability.
Gang Fights - Low priority target in most gang fights, he can take too much damage. Just pay attention to your position, and keep him between you and your other enemies.
- He has a stun that knocks all enemy units within melee range into the air around him, which are then stunned on landing. This doesn't do a great deal of damage, but it can help set up kills. It can stop channeling abilities (Nunu, Fiddlesticks, and Karthus's ult, particularly).
- His second skill (almost his signature move) is a headbutt that knocks you about half a screen directly away from him (stopping if you hit a wall). It can be used from about 5 character lenghts away. The key here is to avoid being between Alistar and the rest of his team (or a tower), or else he can easily headbutt you right into them. This does not stop channeling.
-He has a heal that he can use after an enemy minion dies, that heals him and his allies in a small area. It is not very strong, but can help keep his creeps alive. This is one of the main reasons he is a strong pusher.
- His ult makes him take significantly less damage for a brief period.
Amumu (Mummy)
Usually pretty quiet early (until he makes level 6). High health, moderate damage.
In Lane - Don't hang out near your creeps when he is there, he has a strong AOE nuke that can be activated after taking hits. Try to pace around rather than stand still to avoid a surprise bandage toss. Can be tough to push against. Harass occasionally.
Gang Fights - Low priority in a gang fight, but try not to wad up with your temmates if you haven't seen him ult in a while. Focus him down if he's alone, otherwise just try to avoid him.
- His first ability is a bandange that, if it hits, does damage and drags him to the hit unit. This does not auto-hit, so with foresight you can dodge it. Keep some of your creeps between you and him when laning. If he hits you, your creeps will start hitting him, charging up his nuke (his third ability). If running from him, the instant you see him stop to use this, change directions to try to dodge. This ability has a range of about 6-7 character lengths.
- His second ability slowly ticks away the HP of anyone nearby. Usually people don't use this ability until later in the game. The best counter is staying away.
- His third ability slightly reduces his damage taken, and after he has been hit a certain number of times he can unleash a melee-range AOE damage attack. He will use this to farm, and later in the game to do damage when getting attacked. This is why you don't just stand next to your creeps early, but he can't use it too often in the first few levels.
- Ultimate is an AOE centered on himself that does damage as well as binds heroes to the ground for about 3 seconds. There is a big yellow circle of doom around him when this is happening. If Amumu is in the middle of your team, he is probably about to use this.
Anivia (Ice Bird/Articuno)
Annie (Little Girl)
Strong nukes. Low HP, and no built-in escape mechanism. Be careful when she has little blue swirlies around her, that means her next magic attack (whatever it may be) is going to stun. This comes up every 5 spells she casts. If she's past level 6, it will be her ultimate, and it will hurt bad. Can kill 1v1 if she catches you unaware.
In Lane - If you're in bottom or top lane and she disappears, she's probably over in the grass right next to you. Check the grass, but if her lane partnter starts coming your way, run immediately. Some people put a clairvoyance ward there to counter this behavior. Try to harass her. She is squishy, and has no reliable way of escaping if you focus on her.
Gang fights - She is a high priority target in gang fights, but not above physical DPS. Assume that her ult is available at all times, and don't bunch up.
-Ability one - She has a targeted nuke that deals damage. Fairly standard.
-Ability two - Cone-shaped burst that is usually used to farm. Stay away from your creeps to avoid unnecessary damage from this cone while she's trying to farm.
-Ability three- I'm not sure exactly. A shield that absorbs magic damage, I think.
-Ultimate is an AOE nuke that turns into a creep that can attack independently of Annie. Most Annies will try to hit with this when they're blue-swirling, so that it will stun and Tibbers (the summoned beastie) will get some free hits on you, then they roast you and fireball when you're trying to run. This skill is usually used to initiate a fight.