Hi guys,
first of all, a warm welcome to my (very first) guide. And it's gonna be about the funniest and most annoying champion(depends on in which team he plays): Teemo, the Swift Scout.
You can play the Yordle of Doom at Bot or Top.

Pros:
Poison causes Damage Over Time
Great Early and Mid Game
Getting kills when enemies flee
Easy to learn
Enemies will rage
Good split push with shrooms placed in jungle
Ult can save lifes

Cons:
If not well played, useless in late game
Squishy
Flame is pretty sure

What should I say?
If you want to push, hit minions but you have to get the last hit, so experience is very, very, very important.
If you don't want to push, don't stay around (=easy target for enemy) and just make the last hit.

If the other top laner is better - in general or pushing - play safe and farm under tower. Wait for your jungler, 3 seconds before the gank, get invisible by your passive --> higher attack and movement speed.
Classical Combo should be: Q-W-E
And take the kill! It's a huge advantage in laning phase and a good jungler will let you kill. He should just take it if you mispositioned.

If you're better than your enemy, ward the river and push like hell. Poke him with your blind dart and get him under his turret.
And normally you can get him low hp with your Q-E, so you can go back to base when he is under his turret.

Now it's gonna get interesting: Champs are roaming, Laning Phase comes to an end.
With your fantastic ulti, you can place shrooms in enemy's jungle (little vision) and at top lane (slow the push of enemy).
If your team is good enough try to stay on your lane, so the other team is forced to send at least one of them to you.

But what should you do when he comes?

Option 1: Try to get behind him and place shrooms, then push and kill him with your poison dart, your blind dart and your shrooms.

Option 2: Stay. Get invisible.
2.1.: Let him push, place shrooms and all possible exits, then kill him.
2.2.: Maybe he pings for his team that you're misssing, so he will leave the lane. If not, face him, bait him, slow his pushing.

Split push, when you're team is good enough.
Important:
Wards! Wards! Wards!
When you're team is good enough, you're split push forces the others to send one (or more) champs to stop you --> mid lane can push to base.
If they come, get invisible or use your teleport, so their gank will get useless.
If they don't come, make the inhib and then go to mid lane.
Late game is all about Baron (and a lil' bit Drake).
So one of your team should place a pink ward there.
As a Teemo, you have to make sure, that your push is faster than the enemies' one --> shrooms at mid lane.

Your AD Carry has to be protected.
If they engage blind them, slow them, keep them back and counter-engage with your team.
With teemo, stay in the back and fire your darts like hell. Force them to do something.
It should be clear that you do NOT focus the tank of the team.

All in all, Teemo is a very good in early game.
But if he isn't well played, he gets more and more useless, the longer the game lasts.
This guide is just a elementary one (beta version), i have to get used to all the formal possibilities and i will add some other play styles with Teemo (Teemo the Tank, AD Teemo, etc.)
I appreciate if i could get some feedback, just to know what should i change, what was good and what your opinions are.

Have fun and poison them.