Teemo is a very good Support or ADC. He can get first blood very often and hide to surprise the enemy from behind. Poison is chosen first because it takes a large chunk out of any enemy's health in the first few conflicts. The build can get first blood before minions even spawn. Poison will hurt the enemy but it isn't a sure kill. Make sure the enemy is away from a turret and that you are hidden before engaging. Breaking out of hiding increases your AS for a short period of time in which you hit the enemy champ as much as possible and Ghost if you must to ensure a kill. Teemo is also very good at last-hitting minions with poison. Use this to your advantage when farming and pushing a lane. Teemo can also be played as a support if your lane has another allied champ present. This champ can push the enemy champ back right into your poisoned darts. Mushrooms should be spread out mid and late-game to be used as Sight Wards and to damage any passing opponents. (Be sure to leave a path for minions to get through without triggering the shrooms) REMEMBER: Mushroom slow and damage doesn't stack. Be sure to keep them spaced enough for the slow and poison to wear off before the enemy champ triggers another. Never be afraid to stay in a lane with low health as long as you are hidden and the enemy doesn't have a champ that can locate you.