Welcome fellow necromancers to an experiment rather than a guide.

This is my first guide so bear with me as us grave diggers are not used to such things as laptops and internet!

The aim for this guide is to investigate the purpose of Yorick and how he can bury people alive!
With various summoners in disagreement over his build and play style, I wanted to put an idea to people that works for me but requires an abnormal approach.

I play him like a caster/tank something similar to how I think a Mordekaiser would if they DID NOT HAVE AP SCALING ABLITIES!

Other ideas spring to mind while writing this...
What about Magic Penetration/Physical Attack Damage Hybrid Build? I think this spreads Yorick to far having a little of everything yet mastering none!

So, without further ado...

PROS
Decent tanky stats (note: I said "stats" because of lack of CC. you know what I mean)
Decent Damage Output (team-dependant if built as tank - the Revenant from Omen of Death)
Own group of minions aka ghouls named after the Four Hoursemen - (COOL!)
Fairly flexable build (after two core items)
Able to use his ghouls to evade certain skilshots
Able to control ghouls using "ALT + Right Click"
Ghouls deal Magic Damage
Unholy Covenant PASSIVE!

CONS
Unholy Covenant PASSIVE! (note: ITS BUGGED!! RIOT!! SORT IT!! )
Ghouls deal Magic Damage
Too easy to build in-effective items
Ultimate can cancel spells from other champs (for example, Zilean's ultimate)
A generally weak CC
Heavily Mana Hungry!

Here's one of the first issues with Yorick, RUNES!!

Since I like to be different (or because I can't play like ANYONE else! Here is why I consider these runes.

9 x
Yorick's passive means that all of his ghouls (not sure about the Revenant from Omen of Death) takes 30% of his Physical Damage!

9 x
HUGE mana issues but don't really want to buy mana regen items when other items are required.

9 x
Just try playing Yorick (or any champ for that matter) without magic resist and see what happens! EVERY TANK/OFFTANK NEEDS MAGIC RESIST! PROVE ME WRONG!

3 x
MORE DAMAGE!!!! Nuff said!

The thing with armour pen and magic pen that dosen't sit well with me (not Yorick, cos HE DON'T CARE!) is that of all the research I've done, guides I've read, videos I've watched, NO ONE SAYS THAT GHOULS CAN USE IT! In a nut-shell! I'm not saying its bad or worthless or that there isn't a place for it, just that Yorick's Ghouls is where a good chunk (even 50%?) of his damage comes from! I would rather them do more damage than to just linger longer! The same goes for HP items to give Yorick's ghouls more life allowing their effects to have more time in effecting enemy units!

Unless someone can give me the FULL stats of each Ghoul and what can buff them, I won't use such runes.

How to spend Mastery Points?! Well, I take my runes, amplify where possible then fill gaps with remaining points, resulting in a 8/3/19!

Are you ready for this explanation? cos I'm not! :)
OFFENCE:
No Smite because I'm not jungling.
No AP boost/bonuses whatsoever! It doesn't scale! It's not even used on Yorick!!
Bonus point in Exhaust enables Yorick to chase really well. Helps in escapes too.
3 points in Deadliness because I want to reduce his cooldowns with Sorcery

DEFFENCE:
3 points in Resistance to boost Magic Resist. Nuff Said!

UTILITY:
3 points in Perseverance as standard when using utility tree. Plus Yorick will depend on his [[Omen Of Famine to heal himself, although the additional HP Regen boost is always welcome.

Normally, (because you are pros and I am not) you would put the 4th point into Ghost or Improved Teleport. Since I'm being honest about my play style ( and I suck! ) the extra point in Good Hands helps me lane longer because I'm dead for a shorter amount of time! ( I promise to learn to play, honest!)

3 points in Expanded Mind
3 points in Meditation
This is because Yorick DRINKS MANA! You may think its a good idea to get lots of mana items to cope with this but that is overkill! However, with Manamune in your item build, more mana means more damage! (works for me!!)

This one point in Awareness is to help me not suck. an official and bonafide pro should never need more experience!! I am not pro! Average? Maybe. NOOB? ( < pick of ME with a red x through it!) not any more! lol. Overall, this is one of several points that fit my play style/skill (or lack of...). Feel free to put it to use where you see fit.

Greed is another one of those points to help me play better, not Yorick. Put to use where you see fit.

Quickness is used in place of Boots of Swiftness and to enable the next level of the tree.

Intelligence for the cooldown reduction since I have not got runes to do the same job.

There are many ways and combinations to try but they all seem to rely on the same core stats (Damage, Mana and Survivability), so as long as you cover them in some form, and able to use to the best of YOUR ability, then its all grave-stone...
(did you see what I did there? grave-stone instead of gravey! I made a funny 0.o )

Your Final Items:
Mercury Treads - Magic Resist and Movement Speed. CORE ITEM
- Mana and Damage. CORE ITEM
Banshee''s Veil - Mana, HP, SpellBlock. CORE ITEM
Mana, Armour, CDR and Slow Passive. Very good item to use against a MELEE champ/team.
Damage! Attack Speed boost and its passive act as nice bonuses but all you really need from it is DAMAGE! (Note: It's not a cleaver, it's the shovel when it was new! lol)
lifesteal and Damage! The additional stacks are nice but the lifesteal improves your Omen of Famine and the Damage... Why are you questioning having MORE DAMAGE?! NOOB!

Q:"But wait!!! You have no life items!"
A:Rather than wasting money on HP items for the enemy to eat while they kill my team, AND although Yorick's ghouls gain a percentage of his life, DEAL DAMAGE SO YOU DON'T HAVE TO SUMMON AS MUCH!

In mid game, I can wipe out one minion wave, wraiths, wolves and minor golems in two spells/summons! (I don't mean that I can summon two ghouls and jungle without summoning more!! I mean, at each scuffle, I do my two summons and wipe them out!)

For My Play Style:
Omen of War is to be saved for chasing, pushing hard, ganking/teamfights and kiting
Omen of Pestilence is your only CC spell dealing damage and slowing enemy units. FARM & Chase spell
Omen of Famine LifeSteal Spell. use whenever you need HP or require extra ghoul damage
Omen of Death So many uses! Ganking/team-fights, dropping towers, getting buffs, dragon and baron.
WARNING: Yorick Is new and there is no delay between the Revenant effect and death of the champ that the ultimate was casted on. Similar to Mordekaiser's Ultimate, Karthus]'s passive and [[Zilean's Ultimate where Yorick Gains control (with ALT + Right Click) of a Revenant with Allies Attack Damage. As soon as Allies' HP is gone, they IMMEDIATELY get the Revenant for a short time. If team mates are not aware/used to this style of play, I advise saving Yorick's ultimate for yourself!

In Early Game, YOU DON'T WANT ALL OF YOUR SPELLS UNTIL LEVEL SIX! You also want your Omen of Pestilence to do the work of farming while harassing enemy champs so start off with this and farm hard. Cast Pestilence only on large groups of minions to conserve mana. It's fine if you get pushed back, death is patient!

With the second point in Omen of Famine you mana will go down while your life stays topped up so don't get any more health pots unless you are sucking hard! The fact that you have, or will have, lots of mana to "use" Famine often means you nead less HP pots and visits back to base for anything other than mana and items.

Third Point. How are you doing? if you are getting pushed, skill Omen of War otherwise skill Omen of Pestilence aiming to get one point in Omen of War before the first point in Omen of Death

By the end of Early-Game, your skills should be;
1 x Omen of War
3 x Omen of Pestilence
1 x Omen of Famine
1 x Omen of Death

You are aiming to farm and farm HARD. I can't last hit with Pestilence, so by casting it first then cleaning up manually is how I keep my creep count up. When I'm Pro, I won't have to!
As for enemy champs, Basic Laning 101 - STAY BEHIND MINIONS AND RUN WHEN FOCUSED!

Mid-End Game; the aim here is to max Omen of Pestilence and keep the damage output "Constant". I do not mean spam skills because you do minimal damage depending on items unless you use you ultimate on a teammate (which means you're in a teamfight - CALM DOWN AND CHECK STATS) or on yourself (which means you're getting a buff, taking dragon solo, or downing a tower solo. Both cases will most likely see you go back to base before your next fight).

With this in mind, finish skilling up Omen of Pestilence to max and then choose by asking yourself this question at each "level up";
Can you push easily?
Yes = Omen of War
No = Omen of Famine

By "push" I mean against enemy champ(s) - DO NOT EVEN BOTHER GOING 1 v 1 UNLESS SURVIVAL IS "DEFINITE"! Yorick vs 2 enemy champs = DEATH A THOUSAND TIMES OVER! (Unless you PRO!)

Make sure to level you ultimate whenever it is possible! This skill/spell alone can deal as much as your best DPS can in MAGIC DAMAGE!!! Us on ANY high DPS champ in your team.
Just like Mordekaiser's Ultimate but targeting an ally instead of the enemy, among other things mentioned elsewhere in this "guide".

As far as skills/spells/ghould summons are concerned, there really isn't anything else to add other than, keep an eye on your mana. You have an open invitation to spam abilities but to do so leaves you vunerable once you run out of mana which is very easily done.

In my experience with Yorick it's hard to say what he excells at because at first glance, I would forgive you for thinking that Atmas Impaler, Warmogs Armour and Frozen Mallet is a good idea. Actually, this is a very non-caster build and although the long the game goes on for, the more damage you would do and the long your ghouls would last but anyone taking Maldres Bloodrazor or an AP Carry WILL nuke him hard! Most teams (even versus bots) include nuke AP champs so don't expect to get to run these items often.

The same can not be said about this build because although you're not getting Health items as much as a tank would, you are getting health as part of Banshee's Veil, Armour from Frozen Heart and Magic Resist from Banshee's Veil]] and Mercury Treads on top of masteries and runes.

Remember that this Yorick plays like a Caster/Tank/OffTank/DPS, similar to Mordekaiser in that they both are melee champs with ranged spells able to control their ultimates after casting using Alt + Right Click. Both of ultimates can potentially do masses of damage! And I have seen very few mordekaiser playes use Atma's Impaler + Health Item combo!

So, give him a try before you flame me for being noob or making a poor ... well, like I said to start, it's not a guide! It's an experiment for you to try! It's what I'm using but I am not a highly skilled player like Phreak, Fnatic and Team SoloMid.

Have fun and "BURY YOUR ENEMY'S ALIVE!!!"