Who is Nocturne?
Nocturne is one of the best junglers, if not THE best jungler, in the game. He clears the neutral monsters extremely fast and has the best set of ganking skills in the game.
This is why we play him as a jungler and not in lane.

What do you do?
Your role as Nocturne is to provide your team with a second solo lane, and to then provide all your team's lanes with surprise ganks and interrupts.
By mid and late game, you are the black guy in the middle of the fight dishing constant damage to your enemies so that theyre forced to focus you instead of the nuke.
Ideally, if they focus you, your nuke (ie LeBlanc, Veigar etc) will destroy them all. But if they focus your nuke, YOU will destroy them all ^.^

Pros
Healthy jungle sustain
Fast clears
Ganks everywhere
Good amount of health late game
Constant damage dealer, along with your fear

Cons
Slow MS until your boots and zeal (difficult to chase early)
Can be counter jungled easily, this messes up your route

The Pros for Nocturne far outweigh the Cons in my opinion.

My rune choice is pretty similiar to most other AD junglers.
Attack Speed
Armour
Attack Speed OR Armour
Armour Penetration
Why Attack Speed Marks?
Well.. as you know Nocturne's passive cooldown is reduced by 1 second for every melee hit.
The passive is your greatest source of lifesteal and sustain before you have wriggles, so the more it procs, the safer your jungle is.
Only 10 Ar/pen?
Your masteries give you a fair bit of armour penetration to clear the jungle. Blue golem has 25 armour, so you're pretty much NEARLY doing true damage to him. But the attack speed is more valuable than that extra 5 damage.

You have a choice between Offensive Defensive and Offensive Utility masteries.
Personally for ranked games I choose Offensive Defensive (As pictured)
And for normal games I choose Offensive Utility because it's faster due to the MS buff.
If you're game, you can do that in ranked games too, but I enjoy the extra armour so I have a little more tankiness for the ganks and if they try to counter jungle me.

Smite, obviously :)
I like to take ghost instead of flash because sometimes when you need to save someone with your ulti and theyre just out of range, you can ghost to get in range quick. It also helps because of the moving through units part, when you're in a team fight, they wont be able to outrun or juke you :)
Other viable choices include Exhaust, Ignite, Flash and sometimes Teleport, although I dont recommend it, some people like it for the extra map coverage.

Vamp Scepter
Dont go back to base until 1500g
Wriggles Lantern and Boots of Speed
Dont go back until you have 1765g
Zeal and Berserker's Greaves
Dont go back until you have (ideally) 2100
BF Sword and Vamp Scepter
Pick up your Phantom Dancer when you can and finish off your Bloodthirster
Start your Warmogs with Giants Belt, and then finish it off.
You have a choice here, you can get Atmas Impaler now, or after you get Frozen Mallet.
If you're facing a heavy AD team, get Atmas now, if not, the slow from Frozen Mallet is very nice.
The game should be finished by now, but at this point you can sell your Wriggles Lantern and buy whatever item you choose, whether it be a Phantom Dancer or a BLoodthirster or maybe Thornmail.

Play Video If you cant be bothered watching the video, my route is
Big Wolf (Only the big one)
Blue Golem
Finish the wolves
Wraiths
Mini Golems
Red
(IF PURPLE TEAM)
Gank Top
(IF BLUE TEAM)
Wolves
Gank Top

It's really important to get a kill on your first gank, otherwise you need to stay at top lane until either you have 1500g or Blue Buff respawns. Some people will get pissed off because you're using their solo lane, but tell them not to worry, and try to get the tower. Nocturne is great for early tower kills, and they will be happy if you can manage to get it for them :)

Nocturne is a great jungler and great all round choice for a ranked game. He is also considered a bit of a pubstomper in the same areas of Katarina and Master Yi once he's fed :)
Just remember to trust your lifesteal to keep you alive in mid game, because that's what it's for!
Anyway, enjoy the fastest jungle route and make sure you comment, vote and kick some *** on the Fields of Justice.