In my opinion Support is the second hardest role in the game, Jungling being the first. Supporting isn't fun usually and it's extremely stressful and difficult. It is't for the faint of heart and should be handled by the experienced player. Remember... when you play your first game you aren't some Biofrost level god, you will probably lose your lane first game, unless you play Sona of course. Why Tahm? Shouldn't I play an actual support like Thresh or Janna? You can yes, but Tahm makes supporting fun for me. It makes the most looked down upon role actually worth while.
Tahm is tanky first of all which means he can take damage for your ADC and live to tell the tale. His secondary is a fighter and that he is, but that doesn't mean he can't support. You don't see people telling Blitzcrank he isn't a support. I can't guarantee you will have fun or that you will end up on some CHALLENGER LEVEL PRO PLAYS OUTPLAYS HIGHLIGHT OF GOD- TIERNESS, but I think you will come to appreciate Tahm and his southern charm.

What hasn't been said about Tahm? I don't know, but the main thing about Tahm is that he is annoying. Most of the time if you are bullying a bot lane, they will tilt, afk, or even leave out of frustration because no one wants to have to keep going down lane only to enter some smelly fish's mouth over and over again. How do you play Tahm effectively? Well the first thing I will say is get some friend who plays ADC and duo queue with them, then get some from of voice communication like team speak skype or discord, heck you could even call them on your phone if need be, just have it to where you can speak to them. Now I personally qualify the supports I play into two categories: Aggressive and Defensive. That part is simple, what isn't simple is the fact that Tahm is a hybrid of the two, he can block shots with his large hitbox, he has the best bait potential in the game since the stupid fish has two health bars essentially, he never seems to die, and his AA does way too much, his q hurts even Dr. Mundo somehow, and finally that W is the worst thing for another champion to see. Tahm is weird, he can go so hard on a champion that he doesn't even need his ADC to kill people, yet he works so well bot lane whisking your ADC last moment when they were supposed to die form a turret shot because they thought it was a good idea to dive Shen under tower. I digress, Tahm is an unstoppable Machine that will lead your team to victory.

I shouldn't have to mention that your build should always be flexible and that you should change it up form time to time, but I'm saying it for the newcomers. This build will help you not die, the only thing I ask is that the items that are activatable are used as they are more helpful than you think. Dead Man's Plate is a must have as it is required for Tahm Kench to become a Fish race car, paired with the boots of swiftness it makes for an excellent tool to scare off enemies and get to saving your allies faster or escaping with ease. Iron Locket helps with MR, and again the shield is amazing, When you are in team fights the Iron locket grants extra MR to the whole team making you harder to kill. After that you can decide for yourself to either build more MR or armor or build health for more damage. So, you might've wanted to come down here for an answer on why I would put Warmog's as an extra damage option? Well that lies in his passive which allows his damage to scale of his health, making Tahm one of the scarier Tanks in the Meta.

The bread and butter of Tahm is this, his abilities. He has the ability to make the other ADC and support cry.

Acquired Taste (Passive): The passive to end all passives, so good that riot decided to move it from his ultimate to his actual passive. I don't know why they did that, but it actually helped rather than hindered him. This ability is one of those three hit passives that riot loves, and I will detail how they enhance the abilities, specifically his q and w, and how to use them wisely in the q and w info. It's good to note two things here, First Acquired taste decays over time, so there is a window of oppurtunity, sceond acquired taste can be placed on multiple champions.
this passive makes

Tahm a powerful champion, the tankier you go the more damage you do, so build that health bar.

Tounque Lash (Q): This is a skill shot and an easy one at that, it scales off of his AP and deals almost too much damage. It also slows the enemy making it easy for you to go in for the AA and eventually the W. Acquired Taste procs a stun on the enemy champ. The cool part about this move is that after the stun is done, the champion is still slowed for another .5 seconds. This move can also be used in conjunction with your w to eat a minion from far away. The q is the better poke that he has and it really does hurt too. If you take those AP runes you will be racking up damage against the enemies very quickly, the best thing is to not get carried away or else you might KS your ADC and that has happened to me so many times, as it is just so much damage, but the cc is so tempting, know your limits. max this first for the damage and the slow.

Devour (W): I'm not bothering with this one this is going to fill up an entire chapter.

Thick Skin (E): AKA two health bars, this ability turns

Tahm into the most rage inducing tank in the entire game. This a strange ability, if you take damage you will see a grey health bar appear along side your regular one, if you leave combat and don't get hit, your grey health bar will heal a little bit of your health back, pretty much, if you play it smart Tahm Kench always has health on him. If you decide to stay in combat you can activate the e to gain the grey health bar as a shield for a short time allowing an escape or sustain into a kill.

Abyssal Voyage (R): A variation on the Twisted Fate ultimate, it's very useful for ganking, transporting your allies, and can also be used to finish off a runaway champion who didn't die. This ult used to be better because of the passive, but now it's only ok. This is still a good ultimate just make sure like always you are making the right choice.

This is the most overloaded ability that riot has churned out of their headquarters to date, it is SO OVERLOADED that it makes Azir jealous. OK first things first, this ability scales off of your AP so be wary of insane damage max health damage. Alright there are a few things you can do with this ability

You can eat enemy minions that can be spat back out hitting an enemy champ and placing a stack of acquired taste on the enemy, this has excellent range and can deal decent damage, you might even get a kill.

You can eat an ally, you gain movement speed when you run towards an enemy champion and also your ally can choose when they want to be spat out. They won't take damage while inside you and this move is amazing for saves AND engages.

You can eat an enemy champ after you have three stacks of acquired taste, this will slow you down a LOT so be careful you don't do it in a precarious situation, also as previously mentioned you do a lot of damage to the champion when they are spat out.

I can't stress enough the difficulty of this ability, it does so much for one thing, this move is so good and it is also so bad depending on how you use it. This can kill both you and your ally easily if misused. You can't be stupid with this move, it has an ok CD, but it is still a little too long to consistently save your ADC. I want to re-state the importance of communication, make sure you communicate what to eat, when to eat and when to spit.

Go in lane. Start to spam your laugh. Type in all chat "TIME TO UNCLOAK THE CROAK" or "TIME TO UNBENCH THE KENCH". Laugh as the entire enemy team leaves the game. Tahm Kench is an overloaded champion that can go basically any lane or role and do decently. Tahm Kench is a problem for both you and the enemy team, you are a major liability. Be smart, use your cc wisely, use your w wisely, e at the right time, use your exhaust when necessary. Communication is key to your victory. Use your w to displace champions like the support, and you can also take a champion out of a team fight if necessary. Build Tanky, build health. As Tahm Kench You need to Get fed, that means it's okay to get kills, don't ks, but if you can pick up a kill, do it. Tahm Kench's kit is super powerful annoying, overloaded etc. whatever I said throughout the guide. I main Tahmmy Boy and I have no regrets, he is a joy to play and a nightmare in the right hands. I hope this Guide helps you, obviously, I will try my best to respond to comments so ask away. I know I'm not like a high ELO player and you might think since I'm not an afromoo level player I'm not worth listening to, but I think this will help you out. Check back in-case there are Meta changes such as Tahm's abilities or his item buids.