As Teemo you should know never to dive into battle. Remember your passive, stand in stealth and wait for the perfect opportunity to strike

Camouflage. If Teemo stands still and takes no action for 2 seconds, he becomes stealthed. After leaving stealth, Teemo gains the Element of Surprise, increasing his attack speed by 40% for 3 seconds.

with his passive when i'm Soloing mid. when you're stealted and the enemy solo champion is going mid, you should surprise him, by giving him a stealthed shot. Which will increase your attack speed by 40% for 3 seconds.

Blinding Dart. Obscures an enemy's vision with a powerful venom, dealing damage to the target unit and causing all attacks to miss for the duration. Deals 80-260 (+0.8 per ability power) magic damage and causes the target to miss all of their attacks for 1.5-3.5 seconds.

I really like Blinding Dart, the target will be unable to hit you, for 2 seconds. Popping Blinding Dart, and then Exhaust right after, will be your best shot, at those pesky melee Champions, probaly the best combo against them, thats one of the reasons that i took Exhaust as my Summoner Spell.

Move Quick. Teemo scampers around, increasing his movement speed until he is struck by an enemy champion or turret. Toggle: Teemo's movement speed is increased by 15-35% until he is struck by an enemy champion or turret.

Toxic Shot. Each of Teemo's attacks will poison the target, dealing damage each second for 4 seconds. Teemo's basic attacks poison their target, dealing 8-35 (+0.14 per ability power) magical damage upon impact and again each second for 4 seconds.

Toxic Shot is a very nice passive ability. Its dealing posion damage over time, which is really good. If you are about to kill an enemy, and he flees with very low HP, the Toxic
Shot may very well kill him

Noxious Trap. Teemo places a explosive poisonous trap. If an enemy steps on the trap it will release a poisonous cloud, slowing enemies and damaging them over time. Uses a stored mushroom to place a trap which detonates if an enemy steps on it, spreading poison to nearby enemies which slows movement speed by 30/40/50% and deals 250/475/700 (+1 per ability power) magic damage over 4 seconds. Traps last 10 minutes. Teemo forages for a mushroom every 30/26/22 seconds, but he is only big enough to carry 3 at once.

Pros

-Really good damage.
-Fantastic Farmer.
-Great Carry.
-Good Pusher.
-Can execute tanks fast.

Cons

-Squishy.
-Range enemies with Oracle can destroy his mushrooms.
-Focused in team battles.
-Low HP champion.

Teemo's traps are very useful, always place them. Also try baiting enemies into your traps they deal massive damage and can ensure a kill and can also help out other teammates.

I have experimented with many different builds and as I've stated in the Pros and Cons section that Teemo is a very squishy champion but with these items Teemo has a rather tanky bit of health, this along with Frozen Mallet's cc and your blinding darts ensures survivability. you also have 1.93 atk speed and 344 ability power considerably increasing the damage output of your poison and Noxious Traps. Overall this build brings together the best of 3 three worlds : CC, HP, and High DPS.