Teemo is ranged support/DPS carry champion. He has lot of spells, which are using ability power.

This is build for Teemo, the swift scout. It's build, which I think is ideal. Place mushrooms in bush and at their thirth level they will kill a minion!!!

In this part, I will say you, why I chosed this items.

Doran's blade is best item for start. it increases your HP, Attack Damage and give small 3% lifesteal. It is not much, but it can help. Later it can be sold.

This boots are cheap and thez give 25% attack speed, which is for Teemo very useful. But there is enchanced movement speed only on 2, so you can buy [item=boots of swiftness].

This is very good item in early game. It gives 60% attack speed and great passive. It's active is great, when you are against Pantheon.

This item gives to Teemo lot of damage. It increases crit damage and crit chance. As replacement can be the bloodthrister. It gives you lifesteal and damage.

This is pretty good item for Teemo. It gives Attack speed, Crit chance and movement speed. With this you will be quick as Superman :D

This one has many uses. It gives Attack Damage, Crit chance and cooldown reducion. It have great active :D. It kills.

camouflage This is great passive. When you wait two seconds without fighting, zyou will be stealthed, but you can't move, if you want to be stealthed. After move or attack you will have a buff for three seconds, which give you bonus attack speed.
This ability blinds your target, and he cant do damage to you. It's great against AD/DPS champions { Tryndamere, Caitlyn}. But they can give you damage from abilities.
This ability is good to move quickly around the map. You are very quick and it's good to catch enemies.
This passive ability is great because it cost no mana and it can be upraged by ability power. It deals DoT{damage over time} damage and at fivth level it deals + 165 damage >D !!!!! .
These mushrooms are great trap. It is stealthed and it deals AoE {area of efect}and DoT {damage over time} damage. They does huge damage and slows target. It's good way to escape from enemies.

At start be quick and buy . Then quickly run to top or bot line into bush one enemy's side. Stay in Camouflage until comes enemy champion. Left him too walk in the bush and then shot toxic shots and put Ignite on him. Ignite and some shots makes first blood >D.

Mushrooms are very, very, very, very good because they are stealthed. But be sure that enemy cant see you putting it. Shrooms are useful as wards. Oponent can see them 1 second after putting so be careful, he can destroy it.Is good to put them into bush, or to farm minions [put it in front of them] and to escaping. In early game, when you have low HP, and enemy is catching you, run over mushrooms and enemy will run after you and he will explode >D.

There are good summoner's spells for Teemo. I like Heal and Ignite combination. Ignite is great to first blood and Heal is good to survive longer time in the battle. Ignite has very low cooldown and it does lot of damage. In late game it is not so useful, but still great.

Teemo is great for one vs. one battle. When you are against Mage, you must have shield of . Put on enemy Blinding Dart [q], then some toxic shots [e], then another blind [q], then when he is trying to escape, use move quick [w] and catch him. Before battle place mushrooms on the map, so when he wants to escape, he will explode >D. Is important to use blind, when you are against champs, what have high attack speed. OK, but when they are two ? Make a way of mushrooms and then run to them. On one champion put blind and shoot to the another champ.When you killed him, great and make another blind to second champ. But when zour HP goes down, ESCAPE OVER MUSHROOMS. Then when they are slowed, put on blind and shoot to him. Now he ,must'be killed and run away from another. When you still have HP, you can try to kill the second champ. You get kill or double kill >D.

Be careful, Teemo is great to killing ranged champions. But when are you playing against tanks, you must trz to push them and quickly run, shoot them and quickly escape.
Against mages, is better to buy Banshee's Veil and Be very careful. You must not die in early game and try to use Camouflage, and then use buff, when you have bonus attack speed. Buying wards is not useful, you have mushrooms.
Be extremly carefoul, when is Rammus or Ezreal on their side. Dont shoot stupid to rammus with his shield. Ezreal have long range spells, so try to hide from them.
When is Talon or someone with port against you, stay near mushrooms, they ports to you and on mushroom >D.

In mid lane is Teemo very strong. Put mushrooms at verge of line and barricade wazs from jungle. Hid behind minions and dont run to suicide. Be careful, extremly careful against mages.
When youh have or , you will be better and be more agressive.When you buy 4th item, you will be great on 1vs1.Then put mushrooms in minions wawes.It's free exp and gold >D.