Pros:
[*] Massive amount of mana regen
[*] Extremely difficult to push out of lane
[*] Decent and consistent damage throughout the game
[*] Late game dominance

Cons:
[*] Low damage early on
[*] Mana dependent
[*] Not very strong in jungle
[*] Not the best ganker

I like 23/0/7 masteries, maxing out both penetrations and getting some mana regen.
You could go defensive tree, but I think Yorick does best when his ghouls are eating through other champs.

For my summoner spells, I prefer Exhaust and Ignite. For a melee champ, they simply work the best.
Clarity would be a good option for early game, but becomes pointless after level 6.
Ghost is also good as well to compensate for his slowness at times.
Teleport isn't a bad choice either.
Stay away from anything else, they simply are not worth it.

Max out Omen of Famine first. It is a strong self heal and deals decent damage. This skill is why Yorick is so hard to push out of lane. Put a point in Omen of Death when at level 6, and You can decide whether Omen of Pestilence or Omen of War is more important. They are both good, and your play style will determine which to max out first. I prefer to max out Omen of War first for team fights. But Famine does have a 1:1 AP scale and deals magic damage. Keep this in mind if your opponents stack armor. Hybrid Yorick can work in the right situation.

My rune choices are Armor Pen marks and quintessences, mana regen seals, and cooldown glyphs.
Yoricks ghouls gain the same armor pen as Yorick. And Yorick needs the mana regen, and the cooldown reduction helps him keep his ghouls out.

I generally rush a Manamune. Yorick is mana hungry and severely dependent on spamming his abilities. Combined with Frozen Heart, He gets a good bit of damage, an almost bottomless mana pool, armor, and lots of CDR.

For boots, go Sorc shoes. While odd at first glance, most of Yorick's damage comes from magic damage, and his sustain is based on damage done, so it is appropriate.

Trinity Force is for Omen of War. While it generally deals low damage, with Trinity it turns into a decent burst.

Spirit Visage will buff your heal and add even more CDR. Remember Yorick's passive is only useful if his ghouls are always out.

Lastly, a Bloodthirster will fill out the rest of his AD and make his auto attacks and abilities hit a lot harder.

Atmogs is also a good choice to use if your team needs a strong off-tank.

Basically, once you get enough mana and mana regen, spam your ghouls. They deal enough damage to make a difference, and the bonuses from your passive help greatly. Try getting the Ancient Golem buff often to help keep cooldowns low and mana regen up.

Harass with Omen of Famine and Pestilence, Omen of War is good for last hitting minions. And don't use Omen of Death sparingly. It is not a revive spell, it is the opposite of Mordekaiser's ultimate. Use it on your AD carry at the start of the fight. This is the best way to use it. It turns a 5v5 into a 6v5 for a short time. Also, if your carry goes down, they will be around to finish the fight for a few seconds and help pick up a few kills. This is a great ability to use on teams with long cooldown CC's, because if they blast them at the beginning of the fight, Omen of Death allows your team to finish even if your carry has gone down.

Mainly keep in mind that Yorick is a pusher, and can control the lane easily. He does not do well fighting in the jungle because his ghouls are easily blocked by bushes, as in the won't keep attacking if someone runs into the bush. They will not chase them. Until this is changed, I would not suggest using Yorick to counter jungle and in team fights, try and keep it in the lane.

He can jungle though, and quite well. But his low movement speed and lack of a gap closer makes him less than ideal for ganking out of the jungle. He is much better suited to setting up traps.

If your team does have a jungler, Yorick is ideal to solo lane. He can heal himself quite a bit and keep the enemy at bay with abilities and ghouls. Yorick only gets better as the game goes along.

Yorick is essentially a tanky AD mage. It's kinda a weird way to think about it, but that's what he is. His damage is not coming from his attacks, but mostly from spamming his abilities.

Yet again, this build does not do massive damage early, and it does not make him into a tank. But by mid-game, he can hold his own in most 1v1 situations. Keep in mind Yorick's W and E are magic damage. Meaning you could build a Rylai's and be one nasty slow machine. Plus the added health is nothing to smirk at.

And remember to always build accordingly. If the enemy team has build up Magic Resist, go for more attack damage items. If they have a strong AD carry get Thornmail. If the have a lot of AP, build a FON. This build is just the standard mold that I think is a strong build. But you should always be flexible and ready to change your strategy if need be.