Hey, this is my first guide. I love playing Cho'Gath, and I find him extremely potent, because he has fantastic sustain as well as a fairly high damage output.

1/11/2012 - guide created
4/21/2012 -
Guide updated with more information and a slightly different build. Replaced Rod of Ages with Wit's End because it's cheaper while still adding damage, and doesn't require 10 minutes to charge up to full potential. Also added Shurelya's Battlesong to the build because I decided that the HP+CDR+active make it a pretty solid item. If someone else on the team builds it, it's not as important to build.

Tweaked the runes, replacing flat AP quints with movement speed quints to improve initiation ability. Replaced AP/lvl glyphs with mr/lvl glyphs to make Cho'Gath tankier, since his primary role is to be in the thick of the fight and CC the other team, not to necessarily burst down enemies.

Tweaked the masteries to add CDR and movement speed instead of minor hp regen and exp gain.

Modified the "Items" section to include item alternatives and items not to buy.

Explained why Smite is as important as it is.

Added a suggestion about map awareness.

Early Game

As a jungler, your job is to initiate fights in the lanes. This generally involves hiding in the grass, casting Rupture, and following up with Feral Scream. Once you've done that your main job is to continue casting rupture, and meleeing if possible, and even feasting if they get low on hp, and Feast is available.

Mid Game

When you aren't ganking lanes, you should be helping push towers when you can, and otherwise continuing to jungle. Throughout the game, your primary role should be to initiate with rupture. At this point, you should be letting your AD carry take the red buff (unless they're doing terribly). If you invade the other team's jungle, however, feel free to take any buff you want, unless someone else specifically asks for it. In team fights, you have two initiation tools: Shurelya's Battlesong and Rupture.

Late Game

When the game is drawing to a close, you should be fairly tanky, so you should continue to initiate fights, so that they hopefully focus you instead of your AD/AP carries. At this point, you should leave the blue buff to your AP carry, unless their character has low mana consumption (or is doing poorly), in which case you should take it to enable you to spam Rupture and Feral Scream as much as possible. Almost invariably you should be letting your AD carry take the red buff.

Personally, I like playing Cho'Gath as a robust, mobile, high damage dealer. To fit this, I use 9x Greater Mark of Magic Penetration (magic pen), 9x Greater Glyph of Scaling Magic Resist (magic resist), 9x Greater Seal of Armor to stay alive in the jungle, and Greater Quintessence of Movement Speed to catch enemies in ganks (and to gank more quickly).

Other runes to consider: 9x Greater Mark of Attack Speed to improve early jungling and melee combat, 9x Greater Glyph of Magic Resist (only if you don't have the mr/lvl glyphs), 3x Greater Quintessence of Armor to be more durable against an AD-heavy team or 3x Greater Quintessence of Magic Penetration to deal more damage with your abilities.

I put 12 points in defense to help Cho'Gath jungle and general surivability. The other 18 points, I put in utility to give: bonus movement speed to chase/run, lower respawn times, longer buff durations (very important for a jungler), faster gain to compensate for not getting xp nonstop, and higher hp regen to improve my sustain all game.

I start with a Regrowth Pendant and two Health Potion. This is enough to clear the entire jungle, with or without a leash. When I return, I have enough gold to buy Boots, and possibly upgrade my Regrowth Pendant into a Philosopher's Stone. I prioritize boots because they make ganks more effective and jungle clearing more rapid. When I have enough gold, I upgrade them into Mercury Treads unless the other team is extremely AD-heavy, in which case I'll build Ninja Tabi (and get Mercury's Treads much later in the game.

I then build a Glacial Shroud to make Cho'Gath harder to kill and allow him to spam his skills. Once that's happened, the enemy team should start worrying about you, assuming you can land your ruptures. From there, I build a Wit's End to add additional magic resist, as well as making Cho'Gath's melee capabilities stronger. Keep farming the jungle, and ganking, if the laning phase isn't over yet. I build Glacial Shroud into a Frozen Heart for extra tankiness and CDR, and then look at the other team's composition.

If the other team is AP-heavy, or their AP carry is pretty fed, I'll build a Negatron Cloak. Otherwise, I'll go ahead and build Shurelya's Battlesong for more CDR, HP, and the active ability it has. From there I'll get an Abyssal Mask for more damage and additional magic resist. If the game isn't over, I'll build a Zhonya's Hourglass for extra armor, damage, and a nice active ability. If somehow the game hasn't ended yet, I consider selling off the Shurelya's Battlesong for a Rabadon's Deathcap to give a massive bonus to my damage. I will only do this if the rest of my team doesn't have enough damage.

Other items to consider:
Heart of Gold early on (before Mercury's Treads/ Ninja Tabi) and built into a Randuin's Omen if the other team is AD-heavy (i.e. most of their magic damage comes from only one champion on the other team). Randuin's Omen is nice because it gives CDR, Armor, HP, and a great active.
Guardian Angel can be built in place of Zhonya's Hourglass if you aren't interested in building much damage.

Items NOT to buy:
Leviathan-- A really bad item on anybody. This item psychologically discourages you from being in the middle of the fight out of fear of losing stacks, which is a really bad mentality to have as a tank.
Sunfire Aegis-- the stats just aren't cost-effective considering the passive on sunfire cape doesn't synergize with Cho'Gath. There are simply lots of superior items on Cho'Gath that work with him better.
Thornmail-- the 100 armor is nice, but the 30% reflected damage is pretty inconsequential except against AD autoattackers who have no lifesteal. Frozen Heart simply offers so much more.

At level 1, I get Vorpal Spikes to help clear the jungle as quickly and safely as possible. I get this instead of Rupture because it costs no mana and is nearly as, if not more, damaging. At level 2, I have blue buff and am free to spam Rupture as much as I like, so I get it 2nd. At level 3, I get Vorpal Spikes again to help clear the jungle even more quickly. At level 4, I get Feral Scream to clear the jungle faster and improve my ganking ability.

Once I hit level 4, I start looking for opportunities to gank. From there on out, I prioritize, Feast, then Rupture, then Feral Scream, and finally Vorpal Spikes to maximize my burst, ranged damage.

Generally, I do not choose to gank until I reach level 4, because Feral Scream is an important component to Cho'Gath's combo. It increases his damage output and silences the enemy (which prevents them from using spells to escape). The exception to this rule is if a teammate is in dire need of assistance immediately.

While it is possible to jungle Cho'Gath without Smite, it is basically mandatory to have, because it's crucial to have smite to secure your buffs, jungle faster, and ensure that nobody steals baron from your team. On the flip-side, it also enables you to potentially steal red buff, blue buff, dragon, and baron from the other team if you have vision and time smite right. Other than that, it's important to have a chasing/escaping method. I like Flash because it can help land feast, but Ghost can work as well.

I would not recommend any other summoner spell besides Flash or Ghost, and Smite when jungling Cho'Gath.

Pros

• high natural hp thanks to Feast
• highest true damage burst in the game
• high damage output even when tanky
• naturally recovers hp from unit kills, which makes it easy to jungle with minimal Health Potion usage
• long-duration area of effect crowd-control with fairly low cooldowns, especially with 20-40% CDR in items.
• Feast + Smite means you can instantly kill the dragon, baron, and buffs when they have over 1500 hp left, which makes it impossible for enemies to steal them.
• decent ganking ability, provided you can land Rupture
• looks awesome at max stacks

Cons

• Melee
• Rupture requires some skill and luck to land
• Feast Requires you to be adjacent to your target (not viable to steal buffs/dragon/baron from the other team using Feast
• Having stacks built into Cho'Gath makes him a little hesitant to put 100% into a team fight out of fear of losing stacks.

I start at wolves at 1:40, then go to blue (which spawns at 1:55), then the wraiths, then the golems, and finally red buff. Then, depending on if bottom lane needs a gank, I gank there. Otherwise, I return to wolves/wraiths, and again look to gank. While in the jungle, be sure to use Feast as much as possible. While in the early jungling stages, it is important to use Rupture as much as possible to reduce the damage you take from jungling.

When your blue buff expires, if the other team has no jungler, get to their jungle and steal their blue buff and wolves.

1. When casting Rupture, place it in a location to either cut off an enemy's escape, or in front of your target, so that they either turn around to face you, get hit by rupture, or side step it. If you're positioned right, Rupture almost invariably slows an enemy's retreat.
2. Cast Feral Scream while Rupture is preparing. This prevents enemies from using spells to dodge Rupture.
3. Use Rupture to close distances when attempting to Feast enemies.
4. The key to jungling is map awareness. As a jungler, you don't need to worry about last-hitting like you do in lane, so you have no excuse not to be watching your lanes frequently. It lets you know when people are missing (potentially to counterjungle you), when the enemy jungler has ganked (so you can counterjungle them in the opposite part of the map), and when enemies are being reckless or pushing too much.