Hello!

Here's my first guide for my favorite character, Twitch. This guide is NOT perfect, I am NOT perfect and my english is NOT perfect, so please don't be an ******* ;). This is how I love to play Twitch, but its may not be the way to play him for everyone.

Here what in my opinion, makes Twitch ''hard'' to play:
1st - Gets OOM Really easily, try using your abilities judiciously.
2nd - Remember that Ambush doesn't last hours long. The rank 1 is 10 seconds, which isnt really useful. Care for when it is about to end, cause getting caught in a bad spot usually kills you.
3rd - Twitch is squishy as hell, and a good target to focus since he is slow (305 VS 310-315 average), try chosing your targets carefully.
4th - Don't think that since you dps like crazy, you are invincible.
5th - Oracle's Elixir screws you.

Pros
-Super Fun
-Great Carry
-Can kill squishies in 3 hits.
-Can destroy teams in matter of seconds if your team helps you.

Cons
-You MUST destroy teams in matter of seconds because they will likely focus you
-Ultra squishy (I have 1760 HP at lvl 18)
-Tends to be focused
-The lack of mana early game forces you to make good use of your abilities.

We could discuss about Exhaust but Flash is a must. It lets you get out of the action to Stealth, it gets you of of range of attacks, blinks you forward to attempt to finish your foes, its just AWSOME. Get focused? Start Stealth, flash in the brushes and to safety =D.

Exhaust or Ghost? I prefer Exhaust by far because it will reduce the damage you receive from other carries like Tryndamere and Master Yi, which can REALLY save your life. Well maybe not against Tryndamere =D cause he'll just keep chasing you with his Spinning Slash and Mocking Shout and you'll most likely get destroyed while he's doing Undying Rage.

Other Options

Teleport - Ignite

(PASSIVE)
Deadly Venom : This is how Twitch work. Each time you hit an enemy with your auto-attack, you will put 1 stack of Deadly Venom. Your Expunge will deal more damage for each stacks and Venom Cask will slow 6% more for each stacks.

(Q)
Ambush : Ambush is what will determine if you're a good or bad Twitch . This ability will allow you to stealth, disappearing from the sight of your enemies (Unless they have Wards indeed). The first rank is only 10 seconds, so don't use it stupidly or you might appear right in front of your enemies while scouting.

(W)
Debilitating Poison : This is your MASS SLOW, and one of the only way you can escape from people with Ambush . Remember that you slow 6% more for each stacks of Deadly Venom.

Expunge (E)
Expunge : This is the 2nd best part of Twitch: The ability to say YOU'RE NOT RUNNING AWAY FROM ME F***ER! Expunge deals more damage for every stacks of deadly poison

(ULTIMATE)
Spray and Pray : This skill will make your auto-attacks pierce your enemies, as well as giving it extra AD and range. Teamfight + Spray and Pray + Expunge = TROLOLOL

Greater Mark of Desolation - is a must.
Greater Seal of Attack Speed - I like AS alot, but Dodge is a good choice too.
Greater Glyph of Magic Resist - Magic Resist is always good, more Survivability.

I used to play with 9 Greater Mark of Critical Chance, but ArP Is just so much better.

Greater Quintessence of Desolation : Nuff said.
Greater Quintessence of Critical Chancex2 : Im playing with 2 Quintessences of Crit cause those nasty crits in early game are just amazing.

Starting:

Doran's Blade
I pick the Doran's Blade cause when starting im gonna go for the 1st blood (indeed). Then pickup your Boots and start your Black Cleaver. Choose your targets carefully, in 1v1 Twitch can go down really quickly.

Situationnal Items:

Alot of HP ? Cho'Gath - Dr. Mundo - Olaf - Shen, Go with Madred's Bloodrazor
Alot of Armor ? Rammus - Shen - Malphite? Go with Last Whisper - Yomuu's Ghostblade
Alot of Physical DPS ? Tryndamere - Master Yi - Twitch? Go with Thornmail - Guardian Angel - Frozen Mallet
Alot of Magical DPS ? Ryze - Akali - Annie? Guardian Angel - Banshee's Veil

Things you should know:
1st- Twitch is more effective when playing with friends. Why? Coordination is really important when playing League of Legends. Also, since Twitch is a carry, i'd say that kills belongs to you, so try to get last it on champions using Expunge. This can be very frustrating for people, but your friends should understand better that fed twich is nasty.

2nd- You should NEVER engage teamfights. Why? cause people will just shut you down in 2 seconds. Wait till your tank engage, then choose your targets (Squishies) and blow them down. If they're stacked up, use Prey and Spray to hit multiple targets. In teamfights you might get 2 kills and maybe more!

3rd- There are champions that are better teammates for Twitch. I usually lane with
- Xin Zhao using Exhaust + Ignite + Three Talon Strike + Expunge.
- Taric This is just WOW. Hits + Dazzle + Exhaust + Expunge = 1st blood 75% of the games i've played with him.
- Rammus Hits + Puncturing Taunt + Exhaust + Expunge.
I also recently found that Singed can be an interesting teammate, Fling + Mega Adhesive = Fun.