I started out League using Nocturne and fell in love. Nocturne has the potential to be pretty much anything he wants: jungler, assassin, AD carry, AD offtank, support and even ranged.

Nocturne's abilities are not only offensive, but defensive.

An example of defensive:

You run into a champ that you can't take on like a jungling Nasus who's Q hits harder than a Mack truck. As soon as he sees you, you want to run toward him and hit your W so he doesn't slow you, then you hit him with your E. As soon as he's feared hit him with a shot from your BOTRK to slow him and flash away. As soon as you flash, pop your ghost and shoot your Q to safety. 9/10 you will leave them dazed and confused. Also, if you need a really speedy getaway, ult to a weaker enemy champ or one who's close to one of your turrets.

An example of offensive:

Let's say you have Ryze in your sights and he's far ahead in a lane with none of your teammates in it (he poor, purple fool.) Hide in the bushes and shoot your Q at him then pursue him while popping your W to block any attacks or stuns he can throw at you. As soon as you get in range use your E to fear him. Does he flash away? Flash to him and pop your BOTRK to slow him down or use your Ghost. All the while you're pursuing him, use your Ravenous Hydra as much as possible for extra damage. Time your W just right so that he can't stun you and hit him with your Q as much as possible to ensure he can't get away and that you have increased AD. So you chase him all the way down the lane and he gets behind his turret like "whew that was close" then BAM "DAAARKNESSSS" hit him with everything you've got for an epic kill.

Ultimately, you want to prioritize your abilities. Keep their extra effects in mind like your Q's AD and Movement Speed increase, your W's Attack Speed bonus after blocking an ability or even the little damage your E does over time can be helpful.

One of the greatest things about Nocturne is that his passive heals him every time he uses it and the cooldown is reduced by 1 sec every time he uses a basic attack, keep that in mind. Also, his W increases his Attack Speed by 20%, that's super handy. The first two items you NEED NEED NEED are Berserker's Greaves and Ravenous Hydra. With these two items, your Q and W will excel.

Here's an example:

You're pursuing an enemy from the bushes so you shoot your Q at him, with Berserker's Greaves he will have a ridiculous amount of movement speed as long as he's on his Dusk Trail. Once you get within risky range of the enemy use your W to block an incoming ability, this will increase your attack speed even more than is already stacked with his W's passive and your Berserker's Greaves Attack Speed. Start waling on the enemy as soon as possible so that you can use the granted Attack Speed by your W and heal yourself with Nocturne's passive and the Ravenous Hydra's Lifesteal bonus. Also activate the Hydra for extra AD. This will scare your enemy enough to the point where they start running, then the pursuit begins and you have the upper hand. With BOTRK, Phantom Dancer, Sanguine Blade and Black Cleaver, your AD, Lifesteal, Attack Speed and Movement Speed will ensure a kill or at least some wicked intimidation.

The most important key to Nocturne's farming is the angle you use your Q at. Make sure you hit the minions/monsters in a line so that it damages and affects all of them. Also keep attacking the biggest monster because the Ravenous Hydra's passive will take care of the small minions. Make sure you stay on your Dusk Trail as much as possible to ensure you get the bonus effects (Movement Speed and AD.)

Pros: Stacks a LOT of AD, Attack Speed, Lifesteal and Movement Speed. Has a very useful burst (my favorite is R-W-E-Q but can vary.) Excels in the jungle. Amazing ganking potential.

Cons: Very squishy early game. Champs will more than likely focus you in a team fight.

As mentioned in Chapter 4, you want to make sure you angle your Qs right so that you can have a hasty jungle feasting. You want to spend most of your time in the jungle not only because Nocturne is good for ganking, but your ult can go nearly ANYWHERE as long as you are in the middle of the map.

Are you low on health? No worries. With all that Lifesteal stacked you can just stroll through the jungle and steal health from the monsters then you're on your way back to ganking.

In summation, your Q is top priority, don't forget to use your items to your advantage, look out for ganking opportunities, keep Chapter 2 in mind, but most importantly, GLHF.