Largely Shaco seems to be very much an early game champion, he is ideal for a 20 minute surrender, however using tough items such as Warmogs you can allow yourself to really carry into the late game.

I find runes are very much based on opinion, however i have a standard set of runes i will always use which is:

9 Magic resist Blues
9 Armor Yellows

The reds and quints are the only thing that i change and these for Shaco are ideally critical damage or armor penetration. Generally the armor penetration runes are a more useful on more champions, so i prefer them if you lack IP. This is mainly because critical damage runes are only really useful on Tryndamere/Shaco or sometimes Master Yi.

These masteries are generally fairly self explanatory and are fairly standardized for ad champions.

Many people as with all stealth champions love to get the boots of mobility, but generally i don't find it is a necessary item and find that the little bit extra attack speed makes more difference. This increases his sustained damage and by the time it is getting to a team fight, the boots with extra speed are not actually of any use.
Infinity edge is a must, and the earlier the better. The additional critical damage stacks with you Deceive, this gives Shaco an even greater damage spike, for owning those squishy champions.
Sheen again increases the damage of your initial burst, so makes your Deceive even more deadly. Triforce is what most people say to go for, but the buff that the Triforce gives you is actually the same as sheen, it is no better than sheen, so i prefer to get the Triforce later, as my last item.
I then like to stack as much AD and life steal as soon as possible, and the most efficient way of stacking this are Bloodthirsters.
After this i find it is getting to the point where the insane burst isn't enough to survive. So for the sake of general toughness and appearing like a tough target and not a focus target a Warmogs is a great deterrent. However i have tried an Guardian Angel in this place, but i don't find it is as reliable.
After this finish off with the long awaited Triforce, which is obvious as the rest of the build is complete also it really tops of the build with the 7% movement buff.

At level 1 you take jack in the boxes because it allows you to take either blue or red, and achieve level 2 before anyone else in the game!
After that i like to prioritize deceive over anything else other than his ultimate. As this is his main damage deal and the ability that you will spam. Oddly the mana cost of deceive also goes down with level which helps in the early laning phases.
After deceive and hallucination i like to prioritize two shiv poison, because it increases Shaco's capability to deal damage and to chase.
Jack in the boxes have to come last in this build because mostly they are useless for fighting, no one goes near a bush in a game with a Shaco unfortunately. You can throw them down in team fights, however they tend to not be used, or die from AOE before they get a chance to activate their fear function.

Pros:

High damage burst and easy kills
Likely to cause a 20 minute surrender or easy win due to high kills
One on One this is nearly unbeatable, mostly even Tryndamere looses to this because he dies in exactly 1 shot from deceive.

Cons:

If early laning fails you will be fairly weak into the later game
Late game he drops off massively and is focused in team fights
If the enemy team has a lot of cc then he is easy to counter.

With this guide you may find it just doesn't work, but using this i have won every game for 10 games with a 20 minute surrender.

If you can pull this build off you will laugh when you see those critical hits on a mage for their entire hp bar!!!