Just avoid going into fights with ranged attackers if you can't win because your move quick skill is unreliable in running away. Most people don't realize that magic damage is not only afflicted by teemo's poison, but when teemo's attack inflict toxic shot it also does on attack damage, first a shot of magic damage and magic damage poison. AVOID ANIVIA'S ICE EFFECTS ALL TIME, if anivia can land a stun on you with her stun ball or whatever she can deal double damage on the next shot(ONLY ACTIVE AFTER SHE HAS ULT). If you find that the zhyona's hourglass is really needed switch over to a banshee's veil if you are getting slow, stunned, and etc.
If you find it that you are getting targeted a lot try switching a leveling of your move quick to a blind dart only if you stay near your tower and are getting attacked by physical damage champions.

Pros:
Great harassing early game 1-6 levels.
A skill that blinds. (Great for high damage champions)
A skill that gives enchanted movement depending on the level of skill (Example: level 1 move quick, enchanted movement=1 and etc.)
Shrooms(or satelites depending on skin) act as wards that damage(If teemo is successful in AP his shrooms deal about 1k magic damage. WOOW
Cons:
Easily ganked if hit by a range first.
Very squishy.
Targeted a lot due to squishiness and people's want for MONEY.