Greetings n00b!

Welcome to my guide on how to play Teemo "The Swift Scout"

As Teemo, you chose your abilities depending on what champion you are facing, for example: Versing a Draven, Ashe, Sivir or any ranged/melee (AD) champions you should really max your Blinding Dart first as this will result in them not being able to attack you as they will "miss" all their basic attacks, which means you can attack and damage them, while they can do nothing to you.

If your versing a champion such as Darius, Renekton you will want to max your Move Quick first, as this will lead to them not being able to catch you, there for, dealing you no damage as characters who are tanky generally have a very slow moment speed, and you need to be in close range of them for them to cause you any harm.

No matter the circumstance, have all 3 abilitys unlocked by level 4, and then after that, max the one needed most accordingly.

When your poking the enemy team, and playing aggressively try to hit them with your Blinding Dart then follow up with a basic attack, then run away.
The blinding dart will make them miss their basic attacks, and the basic attack will poison them over time. When poking them, make sure your really harassing them and getting last hits with the minion kills.

When your using your mushrooms, don't clump them together, spread the mushrooms out, and don't forget these mushrooms can be used to ward Dragon and baron, so you can see when the enemy team is going to go there, you can also use them to ward jungle entrances and also you can use them to ward red and blue buff, to see if the enemy is going to take them :)
You can also use your shrooms if your fighting someone, start to attack them, even blind them, then put a shroom directly ontop of where they are standing, this will cause the shroom to explode after a second or two, and apply the damage to them..

Also, dont follow the build/guide like its the bible, change it around to suit the opposition your versing.

Have fun playing Teemo.