Okey, so here it is. I'm so tired of people thinking that all the beefy guys are tanks. Yorick is NOT a tank. He is a squuishy bastard, but I will give you some tips to counter this.

(Yorick seem to be a bit under powered, so this guide will probably be edited to something whole different after he is buffed.)

UPDATE:
*Changed Skill Sequence and Comments to that.
*Added "proof to this build" comment [1/7/2011]
PROOF TO THIS BUILD:

note: I am a sucky player, so these wins could probably be better.

PROS:
+medium distance skills
+Ghouls can harass a bit in early game, making the enemy focus on the ghouls instead of the minions.
+Can gank with omen of pestilence and omen of war in early game, they won't get away from you unless they have flash.
+With this build: Good HP and Damage Output in End-game.

CONS:
-Squishy...
-Constantly out of mana.
-REAAAAALLY bad mid-game, you will be main-target and die in a second. (You should try to play as a support type to avoid this. Stand a bit away and use your ulti on a DPS carry and slow the enemies.)

Okey, I don't have this rune build myself (except the armor part) but this is what I'm aiming for atm. You would want as much armor as possible so you can stay alive in early game. Also you would like the bonus attack damage to boost omen of pestilence and omen of famine. Last but not least, Yorick is ALWAYS out of mana so we will want those 3 extra mana reg.

For the same reason as above (runes) we will want to put some points in defense, we want to stay alive since Yorick is now considered squishy. Then the rest goes into utility. Why you may ask, because of the extra mana regeneration and the obvious cooldown reduction so you can cast your spells more often.

This is probably the part you're most interested of, I have tried different item builds: tank builds, pure DPS build, DPS/tank/skill spam build, but none of them was as effective as this one.

First of you will want to start with and a (you will need it), why you may ask, if I'm squishy wouldn't it be better with ? I would say no, you will want so you can build philosopher's stone for the extra cash income and the mana reg.
So when you hit the right amount of gold you should recall as fast as possible and buy philosopher's stone (time is money) and then use your to go back to your turret. Don't forget to buy as well! The philosopher's stone won't be enough!

After the philosopher's stone I choosed to buy because it will boost your HP and give you a nice cooldown reduction.

Go get some now, Yorick is sloooooow and will need the extra movement speed. After this you should buy instead of completing boots though, because the bonus damage will boost your and .

Complete your (did I tell you Yorick is a slowpoke?) and then go for , more health! More mana reg and health reg! More cooldown reduction! Awesome!

Now let's finish that and boost your skills even more!

Now I would like to get , but this part is kind of tricky. costs a lot to buy and we still have other factors we would like to increase. This is where I actually may go for first and then a . Phage will give some nice health and also some bonus damage while brutalizer will give us some nice bonus damage but also a cooldown reduction! After that you should go for the ] for the huge health boost!

Finish off with either another bloodthirster or . the reason behind two is that I do not consider any other item giving the same amount of AD. The life-steal will also be awesome togethe with omen of famine!

If you meet a strong AP oriented team I would go for before phage and frozen mallet since it also gives health boost as well as a mana boost! Otherwise finish with this item just to make it a little harder for them to kill you.

!!ATTENTION!!
If you feel that you're still going out of mana too fast after buying then throw in a after you bought .

I've noticed that is quite popular in other builds, the reason why I don't have it because I don't like to waste my money on Ability power. But, if YOU are into that kind of stuff, throw in a after/before you buy and then buy later instead of .

USE THIS IF YOU GO OFFENSIVE:
Start of with , it has a good casting range which is great for harass. Also if you meet a ranged enemy and get low on health this skill will help you regain that. Second you should go for , great skill to last hit minions and a good harass skill on melee champions. The mana cost doesn't change so it is worth putting an extra point into this one in early game.
Get depending on how fast your enemies are (movement speed) and if your partner got or not.





USE THIS IF YOU PLAY DEFENSIVE AND WITH A GOOD DPS ALLY:

Start of with so that you can last hit some minions, cast it in bush to scout. If you're with a DPS burst hero you can help him/her gank by slowing them. After that go with . If you get hurt you can just cast it at a minion and it will grant you a good instant heal and a good life-steal heal.
You will want to stick with this combo a while when you're at the lane and not going for kills, just support. When you feel that you got the items you need to take some damage without dying you would want to go for so that you can do some serious instant damage.

TIP: Use the ulti, on yourself in early levels when ganking (unless your partner has mor AD than you) this will confuse enemies but also grant you a lot more DPS.

Remember, you're squishy and slow, you would not want a nasty stun on you or you won't be able to get back to the tower before you die. That's why you should play Yorick as an support type and not a DPS type och character. You should only charge in when the numbers are on your side. Otherwise, grab your DPS buddy and ulti him, now you have two. Slow the target, now he's dead.

The reason for the as champion skill is because most of all, you will be a pusher! You push really fast with and and with all ghouls active you can push a tower with the damage boost.