Welcome to my cutting-edge Hybrid-AP-Teemo!

But why Hybrid-AP?
With the high amount of attack speed you have an high chance to do something important in a teamfight. Your target is the Adc, of course!
In combination with the high-farm-mid you can buy advanced items very soon and make your enemies look like cows!

Pros

-Lane control due to your mushroms
-Awesome farmer (maybe the best in-game)
-Gank-secured due to your mushrooms
-Mobility (Teemo gets on of the fastest champions)
-Blind lets AD's insta-suiciding
-Poison is awesome

Cons

-Squishy
-Not easy to play due to your squishyness
-The itemchoice are important -> hard to choose
-Everybody wants to kill Teemo -> due to your squishyness

[Passive]
Gives you stealth after a short amount of standing still.
When you leave stealth, you get an attack speed bonus.
Perfect for hiding, ambushing and trolling.

[Q]
Blinds your enemy and makes a fight easier for you.
Higher range than auto-attacks!

[W]
Gives passive move speed, active's doubles it.
Awesome for hunting or running.

[E]
DoT!
It ticks four seconds long (every second damage)!
Also it does a huge amount of damage on hit.

[R]
Badass-traps.
Cutting-edge rotating mushrooms with highest technology available in Bandle!
Makes gankers unable to reach you on your lane very fast.
Also you can scout the whole terrain without ONE ward.
Also they do a hugh amount of damage.

Exhaust and Flash!
Ignite is not important because your poison does enough amount of damage to kill your enemies very fast (Combine with your passive].

Flash is nice to escape or to catch running enemies.
Exhaust is awesome for teamfights to make the enemy-adc nearly useless.

You can also take -> Teleport or Ghost, Heal is also a (pretty) good choice.
But it's not that good for Teemo.

LAST HITTING.
The most important thing for teemo.
If you last-hit good you will be able to kill your enemies very very fast in early game, making it extremely easy for you.
And don't forget to place your mushrooms everywhere.
EVERYWHERE.
EEVVEERRYYWWHHEERREE.
Don't forget to save your turret so that enemies run into your mushrooms if they towerdive you.
That is just awesome.
If enemy minions are near your turret, place a trap near the turret so that they die really fast.
If you practice playing Teemo, your turret will fall last.
Also protect Buffs and routes with your mushrooms!

http://www.mobafire.com/league-of-legends/build/teemo-hybrid-with-an-ap-edge-s3-70227
I also recommend you this guide.

Thank you for looking into my little teemo guide! =)