This build is made for a Fiddle-In-The-Middle, or a game with a jungler on both teams. You will have to be 1v1, for this build to work. Solely made for single target kills, in the beginning.

Fiddlesticks is a very fragile hero, specializes in dealing huge amounts of damaging and CC'ing.
Use him wisely and get Bandito Skin ( most awesome skin for him ever!)

I've chosen to focus on AP, so you can hurt as much as possible, chances you meet a tank who stacks MP in solo lane is so small so i wouldn't bother taking more of it.

Standard 9/0/21 caster build, noting new there.

Starting out with MP5 may surprise many but with this item, and the two potions, you will last so much longer, getting your exp to the max! You might wanna get tier1 boots before Codex, but only if you are against a hero with avoidable casts. If you meet a heavy AD team, getting Hourglass before Abyssal Scepter is a good idea.

Getting your Hourglass makes you pretty imba. Crowstorm -> hourglass = Immortal win.

Skillz

I would wait to lvl 3 before doing any aggressive moves is a good idea, Terrify -> Drain -> Exhaust -> wait for CD ( run along if the other player tries to flee) -> get your second Terrify + Drain = Kill ( how's that for a flowchart ;) )

Catch and escape

Using your exhaust is very important to catch people, but also escaping using Terriy -> run -> (if they flash to you) Exhaust is a almost guaranteed escape.
Catching people, i would recommend waiting for them to use their Flash, or getting a Terrify in and if they use flash use your own and then use Exhaust-> Drain to get them.

Crowstorm -> Flash

Channeling your Crowstorm in a bush and then using flash to get to the center is a certain win(Have teammates near for safety, Fiddle is still very fragile.

Avoiding death

Using Drain can both be an effective way off regain health but also a deathtrap, NEVER EVER use drain while you know people are in a bush right next too you, since Drain got such a little range you literally has to be next to the mob to drain it, wait for the mobs to get near a friendly turret then drain it. Avoiding getting gank'd is like any other hero, just remember that you can take **** if you get attacked and CC'd first. Counter attacks can be a valid choice, Terrify -> Drain can change the battle to your advantage.

Avoiding Tower-Diving

Staying at a turret helps you stay alive in the beginning, but you may experience tower-diving, if two people dive you at a tower it is important you wait until they attack you(kiting is very useful here), i would Terrify the one with most interupts, then Crowstorm -> Drain...That'll make 'em run, hopefully. Running towards the base, is usually a bad idea, unless you are certain that they can't catch you.

Personally would i always stay in the back and wait for as many enemies being clustered then jump in. Remember to use your Terrify and Drain after you jump in, else you are waaaaaay to fragile.

Amummu + Fiddlesticks = Awesomeness,

just saying!
Well just general, alot of CC really helps you getting full use of your Crowstorm.

It's all about positioning, getting your Crowstorm and having the element of surprise.
But mainly :Crowstorm -> Terrify -> Drain = Death to almost any hero which is alone.