Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
Teemo is one hell of a champion. He is easy to learn and master.
-"Blinding Dart" is useful for making attacking enemies useless for a few seconds.
-"Move Quick" is handy for chasing down fleeing enemies as well as making Teemo and extremely effective ganker.
-"Toxic Shot" is perfect for farming creeps, and harassing enemy champions.
-"Noxious Trap" is beneficial for slowing enemies that are chasing you, destroying large creep waves and obliterating enemies that have to get two inches from your face to hit you.
***What most people don't see in the Mushrooms is they can be used for practical reasons. You can teleport to them, and use them to guard/scout important areas and ganking routes.
When I play as Teemo, I usually take the middle lane-- and solo. I use the "Blinding Dart" to render my enemies useless for a few seconds while I put a few poisonous darts into them with the "Toxic Shot". Once they start to run away, I cast "Move Quick" to catch up to them. If they don't run away, you can plant a mushroom under their feet while they're attacking you, as long as they are a melee champion, and it will hit them hard.