How do you handle early levels in regards to build, harass, and sustain? I'm great in the late team fights with a mid-full build, but for the first 6-10 levels I'm incredibly squishy, and I have trouble harassing without dying. I end up bot a lot, and the range of other carries, especially Ashe, shuts me down.

I usually start with boots/potions, and I'm trying to build Phage early for the extra HP/chance of slow. Rushing to build Frozen Mallet seems to really slow down my damage, however, versus going straight for Malady and Nashor's Tooth in, say, this guide: http://www.mobafire.com/league-of-le...of-doom-209977

How do you deal with the first levels?

I find Teemo's early game to be one of his strongest points, but that may largely because of when I choose him. I primarily only play Teemo as a counter to top laners who lack in range. Against a melee champion, Teemo shines. You can bully them out of range with autoattack harrass and if they are foolish enough to come at you in an attempt to fight a blinding dart as soon as they are in range to hit you followed by ignite will usually result in an easy kill.

I avoid playing against ranged champions as Teemo.

Shouldn't you also include Rylai's somewhere in your build? I know its a late game item, and that you should never rush it, but it seems better than Frozen Mallet on teemo.

I do think it really depends on your support on bottom. If you have Blitzcrank or any other aggressive support then try to be aggressive too. If not then all you can do is last hit the cs and use your Q(if possible) on your enemies. About the builds.. the one that you post, if i were you i would only use that on top or if I got kills early game. Playing AP teemo on bot is possible but I don't think it would be good like any ADC.

This one really works on bot or top:
http://www.mobafire.com/league-of-le...d-carry-192909

You can also build like a normal ADC with teemo if you go bot.

Definitely rush a Banshee's Veil so you don't get smited whenever you see their jungler.

My usual AP teemo build (top lane)

1) Boots, 3 health pots
2) berserker boots, ward
3) Malady
4) Nashor's tooth
5) Rylai's
6) Deathcap
7) Depends on situation
If they have magic res, I get magic pen.
If the other team is tankier overall, I grab a GA.
If I need magic res, I go with Wit's End.
-I don't go with abyssal scepter because of the AS bonus of Wit's End.
If I need armor, I get Zhonya's Hourglass.

This build tends to be more glass cannon; however, if you situate yourself correctly, you won't be on the bad end of ganks or even in team fights. Sometimes I'll exchange Malady for an early Wit's End depending on the situation. Early AS with AP and pen runes on teemo is top lane gold.

EDIT:

Skills

R>E>Q>W

Your E juxtaposed with AS and AP runes will give you an extraordinary advantage early game, so max that ASAP.
Your Q is amazing against top lane melee champs, so in this situation, get that during your first level instead of E, but still max E first afterwards.
W is handy for leaving or chasing, but it's not necessary to level it past the initial stage early game.
Level your ult for obvious reasons.

Also, Teemo bot is useless imo. There are many better options for ADC, and Teemo just doesn't fit the bill. Teemo is best as top AP. For harassing against a melee champ, get your Q first. Get close enough to them that you can auto attack, and do so. Usually, they will come at you if they think they can score some damage on you (if not a quick kill). Pop your Q right before they reach you, and retreat back. They will only land one auto attack on you, and it will miss. Rinse and repeat, and, after level one, your auto attacks will hit with E as well and cost them even health more for their mistakes. Buy wards after your first base run to avoid being ganked, and save your flash for that very instance. Avoid flashing due to a failed combo, you will usually make it out alive.
After level 6 lane phase becomes a joke for you because you can just place a shroom in the middle of the minions and profit from not only an increase in CS, but also your opponent will most likely back off or take damage. Since you are ranged, this situation is cake.

To look into a ranged vs ranged situation, being aware of your opponents actual range is key. If you're against someone like Vlad, a champion who can out-range you with his Q, then potions, as well as an early E is necessary. DO NOT buy health items early game. You are only wasting your gold and setting yourself up for future failure. To poke, just auto attack every one in a while.

Well, this is how I play mid ap teemo. Start with Doran Shield. This way I have more hp and sustain to exchange damage with enemy. Then I rush to Catalyst to be more tanky. Core items are: AS boot + RoA + Rylai. I have tried 4 or 5 games, and this build only fail me once. That fail is because the enemy used Ahri with RoA + Hextech.

Never go AP teemo mid in a ranked game. You are outclassed by most of the decent mid lanes this game has to offer, especially if you are inexperienced with him.

He's great against melee champs top if you build ap/speed. Spells should be ghost and flash, and do get his run/sprint thing so you can harass and run away when they decide to chase.

mobafire is the worst guides made by noobs for noobs and teemo don't go bot, he isn't an adc he goes top lane