Feel free to read it and give feedback.

Whether you're building tanky or full APC, your role is almost always to use Rupture and Scream as crowd control and to protect your squishies. Cho facilitates team fights, rupturing enemies who are running after your allies, and silencing enemies who are about to cast spells. Cho also ruptures enemies running away to secure a kill.
If you need to initiate a team fight, land a good rupture on the ADC or APC. Bonus points if you can rupture 3+ champs at the same time.
Note: Feast isn't always to kill a champion or to kill a minion. Feast can be used to take a big chunk of HP out of someone who your team is annoyed with. This big chunk of HP taken away will give incentive for everyone else to jump on them and finish them off. Feast should not be available when the team fight ends. Make sure you use it on someone!

When cho last hits a minion or a monster, he gets some hp back. If you're against a player who pokes, it's smart to get poked first and then last hit a minion. This way, you can sustain for a long time. Similarily, get blasted down by a champ first and then take out an entire minion wave with your Q+W if there is one.
*Minions are your moving instant health pots, use them accordingly.*
Also, ult minions early game to get stacks and HP.

If you are attacking a tower with the enemy behind it, the spikes may hit the champion, causing the tower to start hitting you. It's a good idea to click E to turn spikes off before attacking towers.

My most effective spell order for an instant kill: Rupture(Q)-Scream(W)-Feast(R)-Ignite.(if they run away with little health left.)
Q->W->R->Ignite

Mastering rupture(Q) is tricky, and it takes practice and concentration to land them 9/10 times. If you can't, just max scream(W) first.