Hi, I'm AWierdShoe. I've been playing Shen since season 3 (OLD Shen, to be specific), and have played the current Shen since his rework release. I took a break toward the end of season 6 and have finally resurfaced in season 9 and continued to the current season, season 14. This guide will help you learn how to play Shen in all stages of the game.

Shen is currently a decently strong top lane champion at the moment, though his popularity has faltered. Here are the pros and cons to playing Shen:

Pros:

-Strong early laning phase with good damage and shields
-Strong short trades to poke/push the enemy laner out
-Can impact the entire map with Teleport and R
-Allows aggressive play from your teammates with R
-Very good splitpusher with waveclear items, Teleport, and R
-Strong CC with E, good engage but even better peel

Cons:

-Early waveclear is weak without Bami's Cinder/Hydra
-Long cooldowns on W and E
-Loses more extended trades in lane
-Falls off later into the game
-Impacting other lanes can cause you to lose waves, plates, and even full towers
-Cannot do well if his team is behind
-A lot of hard lane matchups (but not impossible)
-Low objective/tower damage

First let's look at the main runes you will usually be running as Shen:

RESOLVE (Primary)

Grasp of the Undying

Grasp allows you to hit hard with your empowered Q autos during trades. As you will be trying to trade often in lane, Grasp is perfect for the lane bruiser that Shen is. It gives you extra damage and sustain when hitting enemies, giving you an edge in short trades, and slowly increases your max HP for the later game tank you will become.

Shield Bash

Shield Bash is the perfect rune for Shen. It gives you extra resistances and damage when you are shielded. Since you will keep shielding yourself with your passive Ki Barrier, Shen gets the most value out of Shield Bash. This makes him even stronger in laning phase.

Bone PLating/Second Wind

This rune slot is interchangeable depending on the matchup. Bone Plating allows you to take less damage in shorter, more burst-like trades (i.e. Aatrox, Sett, Camille). Second Wind allows Shen to regain some health after trading with an opponent laner, which is better against champions that don't tend to all-in too often (i.e. Fiora, Jayce, most ranged matchups).

Revitalize

Revitalize strengthens your heal and shield power, which is perfect for this ninja who keeps shielding himself. It also increases in power the lower HP you are, giving you the potential to turn a close fight around with a well-timed ability. Revitalize also strengthens the shielding on your R, giving you the slight increase that could potentially save your teammate.

DOMINATION (Secondary)

Cheap Shot

Cheap Shot is great on Shen due to the high amounts of CC he has. He can slow the enemy with his pull Q and taunt them with Shadow Dash. Cheap Shot gives more damage to Shen to be on-par with the enemy laner or bully them out. It gives more value than Sudden Impact because your Shadow Dash is on a very long cooldown at the early stages of the game, which Sudden Impact will be relying on. If you want safer laning you could potentially go Taste of Blood for more sustain.

Ultimate Hunter

As Shen's ultimate Stand United is on a super-long cooldown and his build does not consist of a lot of CDR, Ultimate Hunter allows you to have your ultimate up MUCH more often, giving you the potential to have it up when needed. If you're looking for a safer laning phase, use Ravenous Hunter (with Taste of Blood) to give you more sustain.

Against ranged match-ups, you will most likely be constantly shoved in and unable to get the value out of Grasp. These runes are mainly for when playing into ranged match-ups:

PRECISION (Primary)

Fleet Footwork

Fleet Footwork gives you healing and much needed movement speed in lane. Energized auto-attacks allow you to go for last-hits and run away quickly to avoid most of the poke damage, go for short trades and disengage, or run down low-health targets to finish them off. While you lose damage without Grasp, staying alive is much more important when getting bullied in the toplane.

Triumph

Triumph will give you more sustain and survivability during successful ganks or 2v2s, and especially during teamfights.

Legend:Alacrity

Alacrity gives you more attack speed in order to dish out your Q autos even quicker. This can be substituted with Legend:Tenacity against a team with high amounts of CC.

Coup de Grace

Coup de Grace gives you an advantage against weak enemies, giving you the damage to potentially finish them off.

RESOLVE (Secondary)

Second Wind

Again, Second Wind is great for short trades, but it is also great to regain some HP if you get poked by the enemy laner.

Revitalize

Revitalize is still a must. If you want to survive the laning phase, you have to time your passive shields well. The added strength to them will give you more sustain and/or even a fighting chance.

PASSIVE: Ki Barrier

Innate: After completing an ability's effects, Shen shields himself from 60 − 111 (based on level) (+ 14% bonus health) damage for 2.5 seconds. If the triggering ability successfully affected at least one champion, Ki Barrier's cooldown is reduced by 4 − 7.5 (based on level) seconds.

Shen's power manifests as a Spirit Blade that he can control with his abilities.
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The shield appears when:
-Shen's blade has been pulled to Shen's current location with Q
-Shen's W area-of-effect has finished and disappears
-Shen has reached the end point of his E animation
-Shen has finished teleporting to an ally with R

Shield timing is very important in order to block enemy damage and stay healthy in lane. Some enemies may not even expect the shield and be surprised that they lose a close fight due to a well-timed Ki Barrier proc. I like to think of it as a weaker Barrier sometimes. Play around your passive to block key enemy abilities, win trades, or turn fights around.

Q: Twilight Assault

Active: Shen recalls his Spirit Blade to his location. Enemies the blade collides with are slowed for the next 2 seconds when moving away from Shen. Once it arrives, Shen empowers his next 3 basic attacks within 8 seconds to gain 75 bonus range and deal bonus magic damage.

If the Spirit Blade collides with at least one enemy champion, the empowerment is enhanced, dealing increased bonus magic damage and granting Shen 50% bonus attack speed while it is active.
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Blade positioning with Q is super important in lane. You want to try and push your blade up the lane toward the other side so that when the time comes you can easily pull the blade through the enemy and bash them with your empowered Q autos' maximum damage. Shen's early damage is nothing to underestimate in lane. With good blade positioning you have the potential to win trades and push the enemy out of lane or kill them. Since your waveclear is rather weak early on, you'll want to also use Twilight Assault at times to farm minions, especially under tower where it may seem harder to properly last-hit.

A cool mechanic you can do as Shen is a Q-Flash, which is pressing Q and flashing in front/behind the enemy champion (dependent on the blade's position) so that they get hit by the Q-pull through, proccing the slow and empowering the ability.
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It will surprise the enemy and give them much less time to react than flashing first and then pressing Q. This however requires precise timing, and needs a lot of practice to properly get down.

W: Spirit's Refuge

Shen primes his Spirit Blade, creating an area around it. If Shen or an allied champion enter the area, or after 2 seconds, the Spirit Blade creates a protective zone around it for 1.75 seconds, blocking all non-Turret basic attacks that hit Shen or allied champions in the area.
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Shen's W acts like an AOE Jax Counterstrike that works for you and your allies. It can block the following:
-All Champion auto-attacks (including empowered auto-attacks)
-All Minion auto-attacks
-Abilities that proc on-hit effects or act as auto-attacks. This includes:

Ekko's Phase Dive (E)

Evelynn's Whiplash (E)

Ezreal's Mystic Shot (Q)

Fiora's Lunge (Q)

Fizz's Urchin Strike (Q)

Gangplank's Parrrley (Q)

Irelia's Bladesurge (Q)

Kayle's Starfire Spellblade (E, even when upgraded)

Miss Fortune's Double Up (Q)

Senna's Piercing Darkness (Q)

Urgot's Purge (W)

Volibear's Thundering Smash and Frenzied Maul (Q/W respecitvely, though W still heals him)

Warwick's Jaws of the Beast (Q) and Infinite Duress (R, the attacks AFTER he pounces on you)

Yasuo's Steel Tempest (Q, only the first target hit does not take damage)

Yone's Mortal Steel (Q, only the first target hit does not take damage)

Most of these abilities will not proc on-hit effects if blocked by Spirit's Refuge, with some exceptions. A well-timed W can block tons of damage and win you a trade, but it is on a very long cooldown early and you can be vulnerable without it. Make sure you're always right next to your blade if you plan to W. If you're far away from it, you can press Q and then W if needed. Remember that the zone will activate once you or an ally is inside of after 2 seconds, so waiting it out a bit before activating the W zone is an option.

E: Shadow Dash

Passive: Damage from Shadow Dash and Twilight Assault recovers 30/35/40 (based on level) energy.

Active: Shen Dash dashes in the target direction, dealing physical damage to all enemy champions and monsters in his path and taunting them for 1.5 seconds.
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An immensely powerful ability. Shadow Dash can allow you to chase down your enemies and hard-CC them, or it can be used to disengage from a bad situation. As this ability is on a high cooldown early, you should only use it only when you have kill potential in lane or you're currently getting ganked. Shen is vulnerable without E as it is his only disengage tool, and if it is on cooldown you may have to burn Flash in a bad situation (i.e. getting ganked) or you could even end up dead if your opponent knows how to punish you.

A cool mechanic with Shadow Dash is known as a Taunt-Flash, which is when you taunt first and then Flash right at the exact end of Shadow Dash's range towards an enemy champion to extend the range of the dash, allowing you to catch enemies off-guard.
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This requires precise timing to get it down (but not as hard as Q-Flash). With practice it is a very useful tool that can secure kills and open up engages with your team.

You can even taunt multiple enemies at once!
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R: Stand United

Shen channels for 3 seconds, shielding the target allied champion at the time of cast for up to 5 seconds, increased by 0% − 60% (based on target's missing health).

Upon completing the channel, Shen and his Spirit Blade blink to the target ally's location, placing himself and his Spirit Blade between them and the nearest enemy champion. Shen also destroys any projectiles targeting him at the time of completion.
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This isn't your usual toplane level 6 powerspike. When Shen hits level 6, he has no boost to help him in lane with his ultimate, rather he gains the potential to impact his other lanes. Bot thinking of diving? Press R on either the Support or ADC to get a hard engage. Midlane in a close fight? Ult him to gurantee a win. Jungler losing a skirmish? Pull out the UNO reverse card on the enemy jungler. This ult can be used in so many situations in which you can turn the tide of the battle, offensively OR defensively. It can even turn a 4v4 at Dragon Pit into a 5v4, or make it an even fight at Baron if you we're busy split-pushing. Your Stand United channel's faster than the usual Teleport summoner spell, so you'll DEFINITELY get there before the enemy top laner does.

You'll want to be mindful of your initial position when ulting, as hard-CC can cancel it just like how Teleport can be cancelled. A good thing to do is to try and shove your lane out if you're looking to ult a teammate. Even if your ult gets cancelled, the shield will still go through, so it still has the potential to save an ally. Keep in mind that your shield is stronger the lower-HP your teammate is, so sometimes you just want to wait a bit to get the maximum value out of Stand United. Also be mindful of your teammates current position if you're thinking of ulting them, as it could lead to both of your deaths if you're caught in a bad spot post-teleport.

Laning Phase

As Shen, you'll want to at least stay even with the opposing laner by matching them in farming and good trades (especially short ones where they can't poke back). Your goal is to, of course, try to knock down that tier 1 turret before they do (though it's quite hard as Shen's tower damage is very low). You can position the blade up the lane toward's your opponent's side before minions reach the top lane. This will make it so that it is more difficult for the opposing laner to walk up to the wave and contest you without taking empowered Q damage. You'll also want to keep an eye on your teammates in case they need a quick lifesaver with your ultimate, and make sure to ping that it's up. Just make sure to do your best to shove out the lane before doing so, and NEVER ult when you're below half-HP OR a large minion wave is about to crash under your turret. Once you've played it right and gotten the top tower, you should look to split-push.

Mid-to-Late-Game

When split-pushing, you want to be on the side of the map that is opposite of the jungle objective that's currently up. This creates pressure onto the enemy team, as they have to dedicate time and resources and send someone or some people to match your split-push Shen-nanigans. If they don't send anyone to stop you, you can look to take down more turrets and open up the enemy Nexus. If your team is fighting a 4v5 on an objective, you can easily rejoin with Stand United, and if all goes well, Teleport back to the lane you were just at and keep applying map pressure. If both your Teleport and ultimate are on cooldown, it's best to group with your team in case a fight breaks out so you can fight back or peel for your team.

While Shen has decent engage with Shadow Dash, most of his kit is suited to be more of a warden than a bruiser in the mid-to-late game, so it's also good to use your abilities to peel for your squishy teammates (ideally the ADC) and punish the enemy.

In conclusion, Shen is a great toplane pick-up for anyone that wants to heighten their gamesense and map awareness. Though not difficult mechanically, his skill comes from having the knowledge to be ready for anything big happening around the map and to be able to react to it with Stand United. Shen has a very good laning phase, and with an advantage can turn the tide of battle in other lanes, even if his laners are losing. He may not be a carry champion like Jax or Darius, but he looks to assist other lanes in order to get them ahead. The Eye of Twilight will always be watching over.