One of the things that almost any OTP will tell you about their champ is that it isn't as one dimensional as people always think. Teemo is an extremely versatile champion that can be played many different ways based on what you need for your team. Commonly known for being the most toxic champion in the game, a true Teemo main can tilt the enemy top laner into oblivion with a range of different summoner spells, rune pages, and item build.

The most common summoner spell load out to take top lane is flash and ignite. Flash of course being a staple among most every lane and champion, I wont be going deep into depth about why flash. Ignite offers a true damage DOT affect that also reduces any healing from that champion. Combined with Teemo's E, you could fade away kill the enemy top laner at just around 150 hp, Or Late game if they have been hit by a shroom and a basic attack and ignite from Teemo, potentially the fade away kill from about 1500 hp.
Ignite is basically a staple on Teemo because of the kill pressure it adds to the already high pressure champion.
Teleport is very useful for several reasons. It allows you a potential full map coverage with simply 4 seconds of channeling the spell. this can allow you to get back to lane faster so you don't get as far behind and you could even possibly get ahead if your laner kills you but doesn't have TP. It allows you to also have more map presence for a potential dragon or baron fight in the late game while you are split pushing.
Teleport is usually a safer option to ignite and gives you better split opportunities late game while still being able to impact team fights.
Exhaust is the ultimate stay safe for Teemo. It reduces MS by 30% and damage dealt by 40%. If you feel like you're just not at all going to win or you are against a gank heavy jungler, Exhaust might be the choice for you.
Ghost is a potential replacement to Flash. It gives a large amount of MS for Teemo and, when combined with Celerity, Nimbus Cloak, and Teemo W, Teemo will be running faster than anybody can outrun or chase except a Hecarim or Singed.
Smite is an option you can take although it isn't really that good. It will help you with securing cannon minions and has a lower cooldown than any other summoner spell so it synergies well with Nimbus Cloak. Also if you get low on health you can retreat and smite a jungle camp for health. Both the AP, and the AS Jungle items are good for Teemo and Smite Teemo gives the best leashes ever for his jungler.

Though briefly covered in the notes for each rune page, this is a much more in depth guide to what to take as Teemo.
The Dark Harvest Rune page is one of the better ones because of the late game value as well as Teemo's DOT affects make it easier to proc DH usually. Typically a weaker early game than normal Teemo but is 100% the best rune page for the late game damage wise. your shrooms can one shot the enemy ADC from full health with this rune page and full AP build.
Summon Aery is what most Teemo players take and is most recommended if you are relatively new to the champion. it provides a high amount of poke and once you learn how to "catch the aery" (basically moving forward to get aery back faster so you can proc it on the last tic of your E,) you can increase your damage by a lot in the early game. falls off pretty hard in the late game though so use it to really get ahead during laning phase.
Phase Rush is basically just used against perma slow champions that get you in their grasp and then run you down your lane until you die. Nasus. Darius. Olaf. Tahm Kench. Tryndamere. If you aren't against one of them, another rune is probably your friend.
Electrocute along with Phase Rush both have the same method of procing the rune and teemo is one of the best champions to utilize these runes. the slow DOT effect of his E allows you to maintain the window to proc both of these runes much longer than any other champion.
Electrocute is the Bursty rune that has a better early game than DH but a slightly worse late game. Very easy to proc and provides very good damage. Highly recommend instead of DH while still learning Teemo. Remember. Auto Q Auto.
Press the Attack is very good against tank match ups and is the single best 1v1 all in rune for Teemo. Increases his damage dealt in all ins by an incredible amount and is also very good for late game teamfights. Just basic attack the enemy tank 3 times and increase all the damage he takes by around 12%.
Hail Of Blades is a sort of niche rune page for Teemo with only really a few scenarios where is shines. Has good synergy with Teemo passive.
Grasp of the Undying is best for difficult lanes and Tankmo sometimes. Increases your health and deals fairly reliable damage and provides sustain. Teemo's E also keeps Teemo in combat without needing to basic attack and gives a longer window to proc Grasp.
Lethal Tempo is the ultimate AS rune in general and combined with a full AS build, you can shred anybody in seconds no matter how tanky they are.

Basically everything you really need to know is in the Notes for each build i have listed. of course every build is subjective. If you're playing full AP Teemo but the enemy is all AD or only the AD gets fed, feel free to throw in a Zhonyas hourglass. Boots are always subjective to the enemy team as well. Never willingly go AD Teemo unless your team trolls and picks all AP after you first picked Teemo.

Maxing E first is almost always recommended except in a few instanced where you might max Q over E. W or Q next is subjective but I, personally, usually max W second unless I'm going AP Teemo.

WILL ADD MORE IN DEPTH GUIDE IN FUTURE