Almost anyone who has played Cho for a while has come to Terms with his W. Don't worry about someone flashing, they will get silenced and take damage. Someone walks in late? Dmg+Silence. Using Cho's E is the only way to keep damaging enemy champions effectively(ask their turret about this one). Late game your E may do 2x the Dmg of your aa, and at least 1x.

Mid lane is filled with 2 types of Champions: Mid-Long range Mages, and Short-Mid range Assassins. This Guide is focused on the Mage part of that group, although if the assist group is prioritized I'm sure you will be fine.

Here the idea is:
Mage aa~50dmg
Killing unit heal~20-50
E provides the remaining 0-30 dmg back upon the aaing mage.

If you land more Qs and Ws than they do, you win the lane, if not hug turret and split push later. Cho'gath's pushing ability makes him very hard to deal with without a gank. If played correctly you will notice the jungler failing to gank your lane well at least once. They may try again or realize your Q will let you escape or eat them. Om-Nom-Nom, AMEN

The goal is to let your jungler take blue himself. In many ways you are playing a war of attrition, but you have more Health and chances are better regen. Your ult will always deal true damage soo have no fear in casting it so long as the numbers fit(Subtraction).

We all know that mid laners take Flash, Ignite.
TP
One thing, you are playing a top laner. TP is for anytime of game, whether to save your turret, or someone else's. Heck I typically TP to lane after buying RoA, as I might not have boots. Ignite can get you a kill, but TP turns you into a Roaming god. Simply walk out of lane, grab a snack of a ADC and tp back in time for a piece of cake.
Flash
Although Cho'gath benefits from Ghost, ghost does not let him slide thru walls. As Cho'gath is one of few character in the game without some sort of mobility, Flash is needed badly.

Cho'gath's hard CC and High damage and Health, is a lot in one champ.
Cho'gath needs an ADC.
Cho'gath suffers when his is the only tank.
Cho'gath works better with a CC support than a heal support.
Cho'gath works well in the front and mid lines of a team.
Cho'gath works very well against other AP mids, he can take a punch.
Cho'gath does not provide very much range to his team as 3 of his actions(E,R,aa) are melee range.
Cho'gath's Role in every game is to be a Hard hitting CC AOE Anti-Carry Mage.