This (somewhat) in-depth guide will show you how to use Cho'Gath in normal and ranked games. In this guide you will able to see what runes/masteries and the item build that I use with this champions. However, please note that the item build is situational and may be a bad choice if you follow the build for every item, especially if you are failing. As Cho'Gath your main role is to tank a lot of damage in wars, as well as dealing massive burst damage to the enemy. Cheers!

When played properly, Cho' Gath top will be very strong and just about counters every top lane character. Many people struggle with Olaf, Yorick, Darius, etc. in top lane, but with Cho's incredible sustainability and great damage (even at level 1), you are able to ward off these potentially deadly champions. However, in order to use Cho' Gath in the most effective manner, you have to predict where the enemy will be moving and , follow up with a and maybe add a few basic attacks with .

Pros:
Passive makes Cho very sustainable in lane
Massive burst damage
Very tanky
Great CC

Cons:
Not the highest movement speed
May get aimed in wars due to size
may not work as well against high elo players (they can dodge it)

The runes I prefer with Cho' Gath is straight up AP caster runes w/ mana regen. With this set up, you are able to (not necessarily spam) cast your spells many times without the need to go back to base. This allows you to maximize gold every time you are in lane. It also allows to harass the opponent more and dwindle his health until you can eat him.

Masteries are also very straightforward. Basically, you want everything that will increase your damage output and your sustainability in lane.

This passive is probably one of my favorite traits of Cho'Gath. This passive acts as an incentive for you to farm well. It also allows you to stay in lane for a significant amount of time which will maximize your gold earning.
A very powerful spell that will disable your enemies for a few seconds and apply slow. This is probably best used when chasing, running away, or disabling champions such as Galio or Nunu. You may also target this spell to the enemy's ADC so they will not deal significant damage in team fights.
A very important skill in team fights. Try using it on as many people as possible because this has a ridiculous long silence time. It goes up to 3 seconds at level 5, which is more than enough time to kill the AP carry, or prevent enemies from flashing. It can also disable critical ultis such as Katarina, Galio or Nunu without a delay, since the Q has a 0.65 second delay, (in certain situations) it may be more effective to use this spell before your Q.
This passive allows you to deal a significant extra damage with your basic attacks. Remember that this spell stacks with your size, so the bigger you are the larger the area of effect will be. <-- Not that useful. This passive is mostly used for farming early game where you don't want to push your lanes too much with your Q/W, but still want to farm with ease and without much effort. With the runes and masteries provided, you will deal around 40 extra damage per basic attack and 40 magic damage(excluding magic reduction) to foes that are in the line of fire.
Probably the most famous spell of Cho'Gath is his ultimate. This ultimate allows you to deal massive TRUE, burst damage in one spell. Also, if you kill the enemy in the process, you will get a feast stack will increase your size and your health. These stacks will be very important to Cho'Gath because it determines your aggressive you can play and how much damage you can handle. It may be useful (if you want to K.O. an enemy, Q to disable them; W so they cannot flash; and you flash and R him [possibly ignite] to get an easy kill)

PLEASE DO NOT CRITICIZE THIS ITEM BUILD. YOU SHOULD USE YOUR INSTINCT WHEN BUILDING ITEMS, DO NOT FOLLOW EVERY STEP. THIS ITEM BUILD IS ASSUMING THAT EVERY LANE IS WINNING, INCLUDING YOU.

When playing as an offtank, you need to analyse the situation of the game. If the ADC is fat, get as soon as you finish your . If you continue to build AP, it may jeapordise your team in fights, because you aren't able to take the ADC's damage. However, if the AP mid is fat, you will need to get a . This items shouldn't be used against every fat AP. For example, if you are against a Twisted Fate mid, you may be better off getting a . In wars, it will be either your jungler/tank or you that initiates wars, of course TF and other champions with stuns will have it ready to blast you, but Banshee's will counter it and you are able to unload your deadly Q+W+R combo.

This item build also doesn't include wards and elixirs. You may have to purchase wards when your team needs it, or elixirs to give you that bit of extra burst.

The summoner spells I chose when I play Cho'Gath are and . I chose these two particular spells because it allows you to chase enemies, run away from them, and finish them off. Flash is often used to run away or chase down enemies, in this case you are going to do exactly that. In the previous section(skill sequence), I've explained why I chose flash. This is because I am able to get an easy kill with this by flashing and .
I also use ignite because it allows you to finish off champions who are just to tanky for your burst, such as Olaf.

OTHER PLAUSIBLE SUMMONER SPELLS:
When I was very low level (so low I don't have Flash) I always use Ghost, because this allows me to catch up to opponents and eat them :D
This is useful when you are planning to go very tanky. As a tank you need to be able to disable the enemy ADC, and you can do this easily but Exhausting him in addition to your Q and W.
This spell is very useful when you don't feel confident. It is also useful because it allows you to gank lanes very easily (especially if bot lane has a ward in one of the two bushes. This spell also allows you to go back to a tower quickly if you see split pushing or backdooring.

Cho'Gath is probably my best champion in ranked, mainly because I am not too high of an ELO (around 1500). At this level, some opponents may be very good, while others may be utter garbage. Top lanes are usually the medium-high level players (of this range of ELO), because they are confident in winning the lane and is usually their best role. However, at this stage, it is still easy to aim your Q at the champions, because it is in their nature to FARM FARM FARM. If you see an enemy trying to last hit, you can potentially deal a lot of damage in a very short period of time. At level 3, when you have Q/W/E, you can deal around 200-300 damage with these spells and one or two basic attacks, however this depends on the opponents MR. If their MR is very high at level 1-3 (high is around 50+), you may only deal 150-250 damage or maybe even less.
NOTE: Because I do not know the EXACT damage output at level 3, I have given it a 100 damage +/- this may be significant at early game, but should not affect mid/late game, sorryy!! Will do calculations soon.

If you are doing absolutely brilliant at top, you should have your at around 13-18minutes. After your ROA, build a Sorcerer's shoes. HOWEVER, this is assuming that you are confident in your play. If you are doubting yourself (or this guide) you may purchase the level 2 boots after catalyst or before ROA.

When creeping, especially in ranked, it is important for you to last hit as often as you can. At level 2, where you have your E, it will be very easy for you to last hit, however it may push your lane. When you want to Recall it may be useful to use your Q and W against the creeps, because it will push your minions very fast. This will minimize xp/gold loss. Also try pushing until your minions are at their turret before Recalling. If you really do need to recall (very low hp) PLEASE do no hesitate, because you are just going to give the enemy team a kill. When you play like this, you won't need that many ganks from your jungler, which will allow him to gank other lanes or counter jungle. This may be very useful when mid/bot is failing.
When you push please remember to not OVER EXTEND. This is one of the few mistakes that I've seen with Cho'Gath players. They push until tower, and they auto attack the turret without warding the ganking bush at top. This is potentially dangerous, because the enemy jungler can gank you easily. Also remember that when you attack turrets, TURN OFF YOUR because if it hits an enemy champion, the turret WILL attack you.

As an offtank, you are responsible to protect as many of your teammates as possible.
Protection Priority:
1. AD Carry
2. AP Carry
3. Support
4. Others
The reasoning behind this is because the AD carry will ultimately hold the game in his/her hands.

The AP carry will deal massive damage to the enemy, but in the end, AP carries do not always win the game for you. In late game, where everyone has high HP and defensive bonuses, it may be difficult for the AP carry to burst down enemies, while the AD carry will have a much easier time with Right Clicking and of course smart positioning.
Support is your third priority, because they will be the ones saving everyone's lives. For example, Janna has great CC from the Q and W and R, and also has a significant AD bonus from her E. Sona is very crucial in team fights, because she has an AOE stun, if the enemy gets to her before she can ult, it may decide the fight and you may lose. Soraka is able to heal a person in very quick successions and it is a significant amount of HP. With her Q+R+Heal, she can heal a person from half to full hp in less than a second. Other supports include Lulu, which has good CC from ult and Q, and Kayle, which has a game changing ultimate.

In team fights, you may also be held responsible of engaging a war. In this case, you need to prioritize your team before your KDA. This is the problem with many LoL players, they always want at least a neutral score which means that other teammates cannot get fat. If you die, do not worry, because you can gain your R stacks back up quite quickly and ultimately, if your AD carry is able to kill champions in wars, you will win.

WHO YOU LIKE TO PLAY AGAINST:
DARIUS
TEEMO
UDYR
FIORA
KHA ZIX
NASUS
XIN ZHAO
AD SION

IN THE MIDDLE:
YORICK
RIVEN
KAYLE
GALIO
GRAGAS
KATARINA
RENEKTON
WUKONG
SINGED

WHO YOU DON'T LIKE:
IRELIA
NIDALEE
NUNU
GAREN
RUMBLE
TALON
RENGAR
AP SION

This section basically tells you which champions is Cho'Gath strong against. The people who 'you like to play against' are the champions that Cho'Gath excels in beating. The 'in the middle' are champions that need special care. You may need to change your build and skill sequence slightly, depending on how you are doing on your lane. The 'who you don't like' are champions that are potentially dangerous to Cho'Gath, and I will be describing these champions in the next section

Irelia: Because you have good harass, Irelia may use her lower hp to harass you back. She can easily dash to you, stun add a few extra hits with bonus true damage to gain HP and deal a significant amount of damage to you. Also Irelia is very tanky early game and may prove to be a nuisance.

Nidalee: This champion is very dangerous to low level players to find it difficult to dodge her spear. Nidalee's spear is very deadly and can deal MASSIVE damage to you. At level 2, her spear may deal up to 200-250 damage depending on the range. She is also able to heal the damage you deal to heal easily.

Nunu: Nunu is a great top and can beat Cho'Gath if playing poorly. He has great sustainability due to his passive and consume. His passive allow him to get a free spell after a certain amount of hit (7 I think), and if you do not put pressure on him, he can easily harass you with free ice blasts and eat minions easily.

Garen: This champion is very strong in top lane, because he has amazing heal regen. If you harass him, he can just stay back and wait to him health to go back up before he continues to farm. And because you will be farming well with your E, you can push the lane a bit too far and get ganked.

Rumble: Rumble has great harass early game because of the flamethrower. This spell has quite a bit of range, and can deal a lot of damage. Because of this, you will need to be wary on his actions. If he does use his flamethrower, he will probably be last hitting minions, use this time to combo him and retaliate the damage he dealt on you.

Talon: Almost impossible to deafeat. Talon is an amazing hero, he can counter any AP champion in mid or in top. In top lane, you will need to play safe. He can easily deal 200-300 damage to you with his combo, if he keeps doing this, you will be prone to tower dives.

Rengar: Rengar is very annoying in top lane, because he can go in the bush and jump over and over again. Rengars tend to camp at the bush when you are pushing, or when their health bar isn't that high. Because rengar has great pushing power, he can camp the top brush by your tower. This will be difficult for you to farm, because he can just jump out and deal a lot of damage with his combo and retreat back to his bush.

AP Sion: When going against an AP Sion, be careful of your positioning, because he can deal massive damage in a few spells (stun and shield). Also playing against an AP Sion may be hard to harass him because he has a shield that will give him a lot of extra hp.

NOTE: This is all in laning phase/early game.

I know this guide is a bit bland right now, due to the lack to colors and picture, but I will add them later. Cheers!