In my opinion, Shen is THE BEST tank in all of LoL. Why? He has a taunt AND a damage shield, allowing him to go in and draw all of the attention away from the squishies on your team and let them DPS unhindered. And, you can grab quite a few assists while you're at it.

Pros
-Great Tank
-Great Support
-Taunt= great CC
-Damage shield
-Great DPS ("What?" Death Prevention System!)

Cons
-Mediocre damage output
-Banned often in Ranked matches
-Can't be in two places at once
-Sometimes hard to get around the map with (without teleport)

or or or

I go with Teleport and Ghost. Ghost is great for chases and escapes. Teleport allows you to move around a lot more and save towers, which is very easy for Shen.
Your other options are Heal and Exhaust. Heal allows you to stay in your lane and get as much EXP as possible. You want your ult to be available fast so you can help your teammates. Exhaust gives you a much better chance of getting kills and gives you another great CC to work with.

Vorpal Blade - Damages target unit and life taps him, healing allies that attack the target.
Deals 50/95/140/185/230 (+0.65) magic damage to target unit. That unit becomes life tapped for 5 seconds, healing any champions who attack it for 10/20/30/40/50 (+) health over 3 seconds.
Cost
70/65/60/55/50 Energy
Range
475

I always start with this. Good for harassing and surviving. After level two of this ability, I wait until late game to increase it any further, because his other abilities are a priority. Remember, both you AND your teammates benefit from the healing. If your lane partner is low hit the minion they're attacking and let them kill it themselves.


Feint - Shen takes reduced damage for a few seconds.
Shen enters a defensive stance, shielding the next 50/100/150/200/250 (+0.6) damage. Lasts up to 2.5 seconds.
Cost
45/45/45/45/45 Energy
Range
20

Feint is one of Shen's biggest assets. If you can anticipate a harass, it can nullify the damage it would deal. But it really shines with Shadow Dash. In a one-two combo, Shadow Dash an enemy and hit Feint. Most often, they'll run back, especially in a team fight. Feint now blocks damage from turrets, so keep that in mind.


Shadow Dash - Shen dashes rapidly toward a target location, taunting enemy champions he encounters.
Shen rapidly dashes to a target location, taunting enemies he collides with for 0.8/1.1/1.4/1.7/2 second(s).
Shen restores 50 Energy if Shadow Dash collides with a champion.
Cost
120/115/110/105/100 Energy

This is Shen's OTHER asset. Taunting makes you stand out from other tanks in that you not only soak up damage, but you can force them to focus on you. Also, it makes you one of the best turret defenders in the game, since turrets auto-target enemies that you taunt. Use this often to help teammates who need to escape or to escape yourself.


Stand United - Shen shields a target ally from incoming damage, and soon after teleports to their location.
Places a shield a target allied champion, absorbing 300/525/750 (+1) damage for 7.5 seconds. After channeling for 2.5 seconds, Shen teleports to the target's location.
Cost
50/50/50 Energy
Range
25000

Not exactly the most ninja-like ability, but one of my favorites. The best advice I can give for this is to KEEP AN EYE ON YOUR TEAMMATES. If you see one low on health or one that is obviously trying to escape on the minimap, save them! Hit them with your ult and taunt the enemy if you can. This is what separates good Shens from "Best Shen I've ever seen" Shens (I have been called this before). Saving allies not only denies enemies gold and EXP, but you may end up killing them instead. This ability can be a game changer when used correctly.
Also, but don't do this TOO often, Stand United can double as an escape mechanism in a pinch.

0/21/9 for defensive masteries to tank and EXP to get your ult as fast as possible.

Runes

9x Greater Mark of Desolation - To increase your DPS a little. It helps a lot.
9x Greater Seal of Evasion - Dodge is great for going up against DPSers.
9x Greater Glyph of Scaling Cooldown Reduction - Mostly for your ult.
3x Greater Quintessence of Health - To make you less squishy early game.

NOTE: These are just the runes I currently own and they work well. They might not be THE BEST runes for Shen.

Core Items



Other Options



Start with Boots and three Health Potion. Stay in your lane as long as possible. If all goes well, you should have enough gold to go back and get Mercury's Treads and a Giant's Belt. Being a tank, you will be hit with a lot of CC. Treads help you get out of it fast so you can help more. If you aren't worried about CC, go with Ninja Tabi. Then just keep working on your ONE Sunfire Aegis (UNIQUE passive since patch...).
The next items can be in any order, depending on the situation. Force of Nature is your best option against Mages whereas Guardian Angel is good all around or if you're dying a lot. Randuin's Omen is best for DPS heavy teams where Magic Damage isn't going to be prevalent.
Your other options are numerous, although the core items I have chose are the best, imo.
Frozen Mallet/ Rylai's Crystal Scepter provide additional CC in the form of a slow for speedy champs. If you're having trouble chasing, these will help. Thornmail can be used in place of Randuin's or Guardian Angel against DPS heavy teams. When combined with your taunt and Sunfire Cape, the damage stacks up.

Shen is a tank, but he doesn't have much health (for a tank). Nevertheless, don't be afraid to go first in a lane!

Early Game- Pick a lane and stick with it until you get to level 6. At start, go as far towards the enemy turret as you can. If you have your partner with you, a First Blood is very possible. After that the procedure is pretty normal. Kill minions, push, kill champions when possible. Potions, Summoner Spells, and Vorpal Blade will allow you to stay for a long time, so rack up some minion kills.

Middle-Late Game- Later on, go where you're needed. Don't go off alone unless you have your ult ready. You become a great pusher later on. Taunt people that get too close so your team can tear them apart. With Shen you can't be too scared or else you're team will have trouble making progress. If you die, you die. As long as the other team dies more, then it's worth it (disclaimer: I'm not saying you will die a lot, just don't get discouraged if you do).

Overall, you should help teammates as often as possible, which is easy because Shen excels at it. He is not a DPSer, though, so don't get too greedy. I recommend against following enemies past their turrets early on unless you are sure to get a kill.

Shen does take some getting used to, as with any champion. He doesn't get many kills, but he wins a lot of games. And I mean a LOT. So if you want a champion that can head into the heat of battle and live to tell the tale, then give Shen a try.