Shen - With Balanced Steps
Hi there. I'm a long-time Shen player, so I've learned quite a lot about this ninja. I've always found him to be fun to play, even before Riot started buffing/nerfing him. He's a durable combatant with meaningful contributions to teams and team fights at all stages of the game. If you are interested in such a fun and versatile character (I'm assuming you are since you are reading this) then let's move on.
Pros / Cons
He can do well in any lane.
He can fill almost any position in the team (more on this later).
He is extremely durable.
He can turn almost any team fight in your favor.
He's a flippin' ninja :)
He is not a good lane pusher.
He is a poor farmer.
can drain his energy quickly if he does not successfully strike an enemy.
Now, I mentioned that Shen can fill almost any position on the team. This is true to a point. Shen's primary role is that of a tank, but he makes both an excellent solo-top duelist and a good support in the bottom. I'm not a fan of Shen's jungling, but he can do it moderately well. I've even had to take Shen mid-lane more than once, and while I do not recommend doing this if your team has a proper mid-lane character, I was successful at holding my own against the enemy. For obvious reasons, Shen will never be a Ranged AD.
The item build above will serve Shen well in most games. However, League of Legends is a strategy game, and so you will have to adjust your items to best counter the enemy team. I'll explain the items I have listed and what can replace them should you need to.
Doran's Shield is a good starter item for Shen provided he is with a lane partner (either supporting bottom or in top-lane without a jungler). However, if you are solo-laning I recommend taking Cloth Armor and 5 health potions instead.
Heart of Gold is an excellent item for the added health, the gold trickle, and because it builds into Randuin's Omen later. Even if you are solo-lane I recommend taking this as early as possible.
Mercury's Treads are the obvious choice of boots for the magic resist and the tenacity. The only other pair of boots you should even consider buying (and make sure you are REALLY sure you need them) are Ninja Tabi. Only get Ninja Tabi if the enemy team has a lot of AD and not a lot of crowd control.
Kage's Lucky Pick may seem a bit unusual, and it is. I only take this item on Shen when he has a lane partner. The extra AP and gold trickle are quite nice on Shen, but only necessary if your farm is poor (intentional or otherwise). If doing well or in a solo-lane I recommend taking Wit's End or Ionic Spark instead.
Lich Bane is an amazing item on Shen. It provides a nice helping of AP, a fair amount of magic resistance, and the movement speed increase is great for initiating fights or getting out of bad situations. Additionally, the ability to add your AP to your basic attacks after using an ability makes Shen's damage output quite considerable.
Randuin's Omen is an excellent item for its stats, its passive, and most importantly its activated ability. Always be sure to use this in team fights.
Force of Nature not only provides a generous amount of magic resistance and movement speed, but the health regen is amazing. With Shen's considerable health he will be able to stay in the fight for MUCH longer. However, if the enemy team lacks AP, consider replacing this with Thornmail. Only do this if it's the same team that you bought Ninja Tabi for.
Zhonya's Hourglass is another amazing item on Shen. The extra armor and AP are nice, but its active is the most important aspect of this item. Did you just Shadow Dash through the entire enemy team? Zhona's Hourglass will stop a metric ton of damage. Is the enemy Karthus mad about losing the last team fight and pressed R to try to finish you off? Hey look, Shen has denied death better than Karthus. Did a wild Tryndamere appear? You get the idea.
Lastly, Spirit Visage combos nicely with Randuin's Omen and Force of Nature, as well as providing some much-desired cooldown reduction. If you were in a duo-lane, now is the time to sell Kage's Lucky Pick to buy this. If the magic resist would be wasted (against that odd team you buy Ninja Tabi and Thornmail for), replace this with Sunfire Cape, Warmog's Armor, or Rylai's Crystal Scepter.
League of Legends is a team game, and few champions exemplify this quite like Shen. Almost all of his abilities serve the team in some way. Vorpal Blade heals his allies as well as himself, Feint keeps him alive longer to defend his allies longer, Shadow Dash prevents his allies from being attacked, and Stand United not only provides a massive shield to his ally but also teleports him to their location, turning any fight into a team fight.
Shen is a tank, and therefore he needs to be placed at the front of an push or at the rear of a retreat. He needs to be the first to initiate a fight and the last to leave it. Take the Caitlyn bullet. Stop the Rammus power ball. Lead Fizz's shark away from your team if it gets on you. Any amount of damage Shen can absorb or prevent from reaching his allies makes it that much more likely for your team to win the fight. While dying should be avoided if possible, death is inevitable when playing a tank. However, in an ideal situation you should be the only one to die in a team fight if anyone dies at all.
Do what you can to prevent your allies from dying, even if that means dying yourself. Don't sacrifice yourself the 0/4 Lee Sin (though save him if you can get away with it), but if the godlike Irelia is getting surprise attacked by the entire enemy team you'd better make damned sure she stays alive. The extra gold for ending a killing streak can often make a huge difference. In the end, use your best Shen-like judgement to determine whether trading your life for theirs is worth it.
That said, don't be reckless. Shen is tough but he is not immortal. Don't charge into the enemy team without your team behind you unless doing so will ENSURE either a kill or destroying an enemy building.
Tanking does not mean feeding. It means stopping the enemy team from killing the rest of your team despite how much they want to.
Thanks for reading my Shen Guide. If you found it useful or informative, please leave a comment below and feel free to vote the guide up. If you were not satisfied with some aspect of the guide, please leave a comment below suggesting what you think could improve it.
Remember: This is only my opinion on how to build and play Shen. If you find something else that works better for you, great! I look forward to meeting you on the Fields of Justice.