Thanks to Searz for the awesome guide format! You can find it here.

I will not go through what the abilities do. It can easily be learned by reading the ability tooltips and simply using the spell.

Mouse-over any items or abilities to see their tooltip.

Legend

Cho'gath, is a tanky mage who does quite a bit of damage with his ult. He is mainly played solo lane top, or 1v2 lane bot. Sure you can play him full out AP, but I think Cho'gath is made to be a strong tank who can dish out damage even when being focused.

You want to get more in defense, since you are really tanky. You can switch around with MR and Armor, because the other team may have more AP or more AD.

I like the health regen, because combined with you passive, you can stay in lane forever. Again, if they have a lot of AD, pick Evasion, because then dodge will help.

50% damage from minions helps when you are harrasing, but blocking 2 physical damage is always good.

Scars just give you more HP. And since you are a tank, HP=Good stuff.
Attack speed and AP. Vorpal spikes anyone? 4% reduced damage is just another component of your tankiness.

Perseverance is a good mastery if you know your not going to die a lot.

You want to get more in defense, since you are really tanky. You can switch around with MR and Armor, because the other team may have more AP or more AD.

I like the health regen, because combined with you passive, you can stay in lane forever. Again, if they have a lot of AD, pick Evasion, because then dodge will help.

50% damage from minions helps when you are harrasing, but blocking 2 physical damage is always good.

Scars just give you more HP. And since you are a tank, HP=Good stuff.
Attack speed and AP. Vorpal spikes anyone? 4% reduced damage is just another component of your tankiness.

Perseverance is a good mastery if you know your not going to die a lot.

Q > E > E > Q > E > R > E > Q > E > Q > R > Q > W > Q > W > R > W > W

Why do I go Q first?
Q is great for an early game teamfight. It can pick off someone for an easy kill, and combined with another stun or knockup, it can prove fatal to many members of the team. However, if you go straight to laning, then pick up E first then Q.

If you are laning against Mordekeiser or Morgana, you want to pick up Feral Scream earlier, for the silence. Of course, level up your Feast EVERY level you can! You don't want to miss out on a free 1k true damage!

According to my calculations for MR and Armor I have the following:
25 MR from boots
76 MR from FoN
55 MR from Wit's End (max stacks)
57 MR from Abyssal Scepter
06 MR from Resistance
Rounded down -> 13 MR from runes
30 MR from base stats (according to wikia)
That totals 255 MR.

99 Armor from Frozen Heart
75 Armor from Randuin's Omen
02 Armor from Hardiness
Rounded up -> 13 Armor from runes
Rounded up -> 23 Armor from base stats
211.19 Armor in total.

What you want to do is farm as much as possible. I know this is very redundant, but with Cho'gath, you items take some money, and also last-hitting gives you HP. So if you have to walk past someone to get a last hit, do it, because you also get HP back.

Cho'gath has very strong laning phase, because of his passive. Therefore, abuse it. The only person who can out heal you is Warwick or Udyr. Against Warwick, play more passively, because he has more heal than you. If he walks up to you to Q you, just silence him and laugh.

Udyr is more tricky. You can't exactly silence his W. So just play patiently, and call for ganks from mid and/or the jungle.

I have noticed Cho'gath dominates Corki a lot of the time top lane.
-You can TP out of almost any Nunu gank or Warwick gank (after ultimate) for and easy getaway.
-You do SO MUCH damage with a Rupture>Flash Feast>Silence>AA. If you get a jungler to help, boom, he's dead meat and 300g for you.

If you are laning against J4, then just Feast minions when it is up(don't do this before dragon though. 1k true damage is a secured dragon.). This will give you an enormous size and force to be reckoned with.

Try to get dragon by TPing in and killing it with your team. Feast last-hit it to secure a free dragon.

As Cho'gath, you want to sit at the front of the fight, and do damage with your spells, and perhaps silence the AP caster. You are VERY tanky, so play with the mindset that no one can kill you except their 5 members combined, and that you have teammates. You should Feast a main target in the teamfight, say Ashe or Brand. It's ok to Feast a tank, but try to get the squishy. Your Vorpal Spikes should ALWAYS be on. It does quite a bit of damage to teams clumped up.

Your main goal is to protect your squishies. You should try to silence an Akali who jumps onto your Ashe. If Olaf gets too-close, tell you team to focus him down to make the teamfight at 5v4.

Since you are the tank, and you probably do not play on a organized team, you should call the shots. You initiate, so it only makes sense. Tell you team when you're going to go in, so they can back you up. Or if you have Ashe, try to land an arrow before jumping in.

Trick #1- I'm not absolutely sure, but I think you can silence Sion's shield. I need confirmation, but it happened in one of the pro games (CLG vs. OGB or something).
Trick #2- People underestimate Feast's damage. Rupture them, Flash Feast. Free meal.

Tip #1- Don't save your Feast if you know you're going to baron and may have a baron fight because Feast can secure baron easily.
Tip #2- Never forget about Teleport. You can escape if your assailants have no stun.

As a main tank and not a big carry, you should find it easy to buy 1-2 wards on your trip back.(don't have to, but if you do it'll be a big help for your team too) Put 1 in the three-bush at top, and one near baron. Also, try to ward the three way with wraiths and mid.

Tell you support to also ward the bottom bush and dragon. Later on you can ward red to see the spawn time, or just get a lucky kill.

Remember, either you, the jungler, or the support should get an oracles.

This is where my Cho'gath build ends. I hope you have enjoyed it, and please leave feedback on what was good and what was bad. I hope you can win some games with this build, and be happy.

SageAdvice