as soon as the minions get to lane you want to start farming right away. if properly done Teemo can take of in the early game and be a terror through out the rest of the match. Getting to level 2 before you lane opponent can be a major opportunity to start poking. remember Teemo is not all about getting kills, annoying and bullying you enemy can make them tilted and throw off their game so poke as much as safely possible. however getting a early start to you kill count will help the next few minutes

by this point you should have your shrooms... USE THEM AS MUCH AS POSSIBLE they are a great way to start a push and can be an even better saving grace in those dying moments. if you did not manage to score any kills in the first few off spawn minutes the early game can be a nightmare, at this point learning how to poke without trading can be a major game changer if not (good luck. if your lane partner has a root ability you are still safe, getting kills should be as simple as poking with Q till the root comes then taking advantage and going full force

if you have been successful in the last few steps by this point you should have a few kills under you belt and be well on you way to that core build. this is when it is now safe to trade with opponents (as long as they are not fed). having a high AP and magic penetration means that trading blows with anyone should be worth and if they are not tanky enough end in a kill for you.

this is when you should be going for those extra items. your AP is insanely high and people fear you 1v1 or 1v2 should always be in your favor if you know how to shroom correctly, if you do not feel like fully engaging in a team fight go back to you early game ways of throwing shrooms into the battle then poking and running, your poison from the E passive will do alot of the work for you :)