Pros
- Excellent farm capabilities
- beast early game
- great ganker
- Ranged DoT ending in a fear
- Spellshield blocks EVERYTHING
- IMO better chaser than Yi, and murders carries like Yi
- Ulti causes discord amongst enemies

Cons
- Squishy
- not much cc
- Ulti can be line-of-sighted
- No real tower-diving capabilities

I grab clarity and flash almost exclusively. With the mana regen from talents + clarity, you can almost spam Q when needed, and a good clarity/spellshield combo when low on mana is an excellent bait.
Flash just highlights Noc's ability to chase, and flash + dusk trail over a wall is a perfect getaway.
I know most people prefer Ignite on melee fighters, but I find Unspeakable Horror works almost as well with it's range.

Noc's bread and butter, makes for great chasing, huge bonus dmg especially early game, and good for getaways. Max this, and don't be afraid to blind fire at enemies who LoS you.
Noc's defensive utility, the shield blocks everything; Karth's ult, Caitlyn's ult, tank's taunts, etc, and gives bonus attack speed when used against an ability. Requires good timing as it doesn't last long. Plus, the bonus attack speed frees up early gold for heavy hitting items. Max this second.
The fear can interrupt channeled abilites, and does a bit of damage on the side. I've had a few kills on champs running away tethered to this. The damage isn't great, and the tether is too easy to break for this to be maxed sooner.
This ult is scary as hell. Sends champs running to bushes or in groups predictably, which a well cooridnated team can take advantage of nicely. And if they don't break LoS, easy kill for Noc.

Laning
He's pretty easy to lane with. Harass like mad with Q, farm like crazy, and use your spellshield to block the big damage abilities. When attacking towers, blast Q through it to gain the bonus damage against the tower, as well as crippling the minion wave coming in to reinforce. Because of his penchance for farming and first blood, I find I can easily get BF Sword as my second item, followed by boots.

Mid Game
Often, by the time I've hit lvl 6, I'll have BF Sword, boots, and perhaps Vampiric Scepter. This means, ganking time! I'll usually go for mid, then swing town to the other lane. Squishies in mid don't stand a chance, especially if your team's mid has a slow or stun. I will usually go for red buff if we don't have a jungler, as clarity provides me with all the mana I need. Continue ganking, farming, and pushing towers as needed. Should have a second BF Sword by now, so farming is simple and will barely slow you down as you travel from lane to lane.

End Game
Hit the carries. Nocturne is one of the best anti-carries with his +60 bonus damage while on his dusk trail. If the enemy team has more than one champ with armour stacked, I grab Black Cleaver instead of Phantom Dancer, but he's still not great against tanks. Noc can hold his own, but relies on CC when it comes to hunting down tanks.

So this is my first guide. After playing Noc since launch, I've had great success with him. Excellent anti-carry, and a total beast early game.
With the armour pen runes, Doran's blade, and the dmg bonus from his Q, he hits from almost flat 100dmg at lvl one, which makes him one of the best champs for first blood, and even double kills.
Instead of jungling, I prefer to lane him as he can farm almost better than mid and can gank mid fairly easily.
Hope you find this useful, and feel free to comment.