Hi,
Shen is a tank and should be played as one. He's a nice Babysitter and a good initiating tank due his AOE taunt. He also saves alot of f* lives! Play him correctly and your chance of winning is increased over 9000!

Ki Strike
Every 8 seconds, Shen's next attack deals bonus damage. A tiny little burst early game.

Q=Vorpal Blade
Deals 50 / 95 / 140 / 185 / 230 (+65% of ability power) 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 (+20% of ability power) health over 3 seconds. - Harras spell early game and helps you stay on lane longer :)

Cost 70 / 65 / 60 / 55 / 50 energy | Range 475

W=Feint
Shen enters a defensive stance, shielding the next 50 / 100 / 150 / 200 / 250 (+60% of ability power) damage. Lasts up to 1.5 seconds.

Cost 45 energy | Range - Aborbs fairly amout of damage early - mid game with enough MR or AR even late game :P

E=Shadow Dash
Shen rapidly dashes to a target location, Taunting enemies he collides with for 0.8 / 1.1 / 1.4 / 1.7 / 2 second(s).
Restores 50 Energy if you hit a champion.- try to land it or you will be screwed because low energy pool

Cost 120 / 115 / 110 / 105 / 100 energy | Range 25000

R=Stand United
Places a shield on both a target allied champion and Shen, absorbing 300 / 525 / 750 (+100% of ability power) damage for 7.5 seconds (Shen's shield absorbs half as much damage). After channeling for 2.5 seconds, Shen teleports to the target's location.- This is what Shen makes Shen your mates will love you:P

Cost 50 energy | Range unlimited

Basic tank runes with live quints armor and mr glyphes etc.

Tank masteries including some extra life and reduced damage.

Alternatives:
Thats a great alternative for dooing some nice combos with taunt and flash
also working fine for laning

I'm starting of with a ruby crystal for a bonus life of (60 from masteries , 100 from runes and 180 from ruby crystal) 340 for the start which is great. Then picking up Mecury best boots. Then finishing Agies of the Legion. Then buying a giant belt for some additional HP. Moving on to buy Force of Nature. Finishing the belt to a Sunfire Cape. Then buying a Banshee's for the NICE passive.(ignore the loss of mana its a great mid-late game choice) Finally buy a Thornmail.

FACING HEAVY DPS:
-Ruby crystal
-Mecury
-Agies
-Thornmail
-Sunfire or Randiums Omen
-Wamogs
-Banshee's

FACING HEAVY AP:
-Ruby crystal
-Mecury
-Giant belt
-Force of Nature
-Banshee's
-Sunfire
-Wamogs

not much to say just last hit with your Q spell and your passive.

If you see a Mate is facing 1vs2 or is in trouble because he has low life because of Teemos mushrooms and is almost diying cast your ultimate on him .

If in fight you Port on your Mate,use heal, pop on W then use E to taunt all and use Q to do some damage with your allies. If needed use exshaust on the enemy who is dealing the most dmg to reduce it.

ALSO IF YOU ARE IN TROUBLE TRY TO POP ON W IF POSSIBLE AND TAUNT TRHOUGH WALLS TO ESCAPE EASIER.

NOTE: Your Ultimate is channeling one so it can be interupted by a stun or a taunt.

If you have some improvement or ideas let me know in the comment section below.