So...my first guide is here! Everyone wants to own as Teemo, but not everyone can do that. Well, this guide solves everything! Just be sure to read it through, and the forever hunted Teemo will become a hunter. Don't watch the Ability power ^ up there, since it's bullsh*t. You will have over 400 because of it. Believe me.

+ Very flexible
+ Insane damage output mid through late game
+ Works perfectly as an ambusher
+ Can get tons of kills (20/5/10) if played correctly
+ He's a midget, and all midgets in LoL are OP

- Small range
- Very, very, very squishy
- Often focused for his lack of survivability
- Everyone hates him :(

Farming is the most important thing for you. Try to get to the middle lane, since you won't be able to farm that good in lanes with other players. If your foe has a long range (Karthus, Orianna etc.), just wait until the lane pushes and farm near the tower. If enemy is not aggresive and both of you want to farm, farm until level 5 and then poison the sh*t out of that champ! Anyways, back to farming. Farming as Teemo is quite easy, the cheapest trick is to one hit each creep in the wave with your E activaed and just sit there until they get low enough when you can last hit them. Remember, your E does bonus magic damage besides poisoning the taget, so last hittinh is really easy. If you are really good with timing, you can shoot at creep when it's attacked by your minions, and the poison will kill it. Be creative!

Mid and late game farming is even easier than laning phase. You just get to a huge*** creep wave and let them taste Teemo's blowgun. They will die pretty easy, since, god how I love that E. After 20-30th minute of game, you will have ton of time to farm. Just scroll down and it will be explained...

You want to mix ability power with a little bit of damage and attack speed. I don't have to say anything more, just copy the masteries like everyone here does.

Yay! Here it is! How to own as Teemo. It's pretty easy. After the laning phase is done and everyone runs through the map like ******ed, it's Teemo's time to shine. Start by planting shrooms into spots like bushes etc., best shroom locations are in this map:

http://i45.tinypic.com/34zx3qp.jpg

The red dots indicate shroom locations, and the green lines indicate the paths on which you are going to put the rest of your shrooms. "But I don't have that much shrooms!" Indeed. But Teemo is a scout and that's the first thing you are going to do when the laning phase is over. You will be just running around the map, helping teammates and sh*t but your primary target is to find out where your enemies are spending their time - Nashor's riverside or dragon's riverside. After you find out, just plant everything you have in that river. Where are you going to plant them? On the green path. As you can see, green paths are connected to some shrooms in bushes that are visited most frequently. So just make a path and when your foe goes into a bush and eats your shroom, he will think "aw man, again! Nevermind let's just go" and he will step right into 2-3 more shrooms before he realizes that it's a bad idea to continue. Remember: shrooms are your biggest friends and it you get shroomkills a few times in one match. Remember2: red dots on the map are your PRIMARY locations to plant shrooms into. So try to get your shrooms into most of the places and then start to build your little path. Remember3: always watch the minimap, if you see the mushroom disappear, that means your foes are there (yeah, it doesn't take a f*cking brain surgery to figure that out). Remember4: NEVER, NEVER EVER PUT ALL OF YOUR SHROOMS INTO ONE PLACE. THAT'S THE BIGGEST MISTAKE. EVEN IF 10 SHROOMS EXPLODE, IT WILL HAVE THE SAME EFFECT AS ONE EXPLOSION. So that's why paths, not clusters. Now, I know how this sounds but...
You won't be able to help your teammates. Teemo is an assassin character and more of a 1v1 champ than teamfighter. Let's just face it. You are going to die in first 5 seconds of teamfight and you can't do sh*t with it, since your range gets you too close. I don't say that you need to let your teammates 4v5 all the time, but you are needed to be somewhere else. That magical place is called river where everyone goes since they are lazy to go through longer lanes. Your main job is to plant some shrooms and wait in bushes stealthed with your passive. This is not going to work if your enemies are not ******ed and they will buy Oracle's elixir. But most of the time they are, so it's cool. So you are just sitting there and some random dude walks straight into 5 of your shrooms. Half of his HP is down and he's royally pissed off. That's the time when you are going to run out of bushes, shoot 3-5 shots on him, ignite and then run the f*ck out of there. Shrooms damage+your E+basic attack damage+ignite=kill for Teemo.
That's just how you are going to get to end of this masterplan. After you get almost everything from required items, you are ready to kick some serious arses. With these items, you are going to get their HP down with poison and attack damage, not speaking of almost 2.000 attack speed. I mean that's just insane, and if opponent can't one shot you, you have pretty much won the fight.