Xin Zhao has amazing DPS and a strong gap closer that makes him a great assassin. In the current meta, AD assassins are very strong mid laners (Take Zed, Talon, Kha'Zix for instance). Xin Zhao high damage and knock-up are great for destroying your squishy opponent.

NOTE: This is a guide for experienced Xin Zhao players. Do not use this guide to learn how to play Xin Zhao, use it to learn how to play mid lane, instead of jungle or top.

Pros:
-High Burst
-Knock-up
-Gap Closer
-Little damage needed to be strong.
-Has great sustain with life steal and the passive on Battle Cry.
-Amazing turret taker.

Cons:
-Escape moves are a major counter.
-Blinds counter.
-Gets poked easily while farming.
-No escape.

Level 2 is when you make your move. Dash at them with Audacious Charge and hit your Three Talon Strike. Ignite if they are low enough.

This will cause the enemy to either
A) Die
B) Use summoner spells to escape.
C) Get away with little health.

In all three scenarios, you win. Do this as many times as you can until they learn you shouldn't be messed with and get zoned, while you free farm.

Standard runes. Armor Penetration, Armor, Magic Resist, Attack Damage
If you don't need the magic resist, you can replace it for attack speed.

21-9-0. Full damage for maximum hurt.

Start:
Long Sword 2 Health Potion, 1 Mana Potion, and Stealth Ward

Standard Build:
Blade of the Ruined King, Zephyr, Ravenous Hydra, Randuin's Omen, Spirit Visage

Boots:
Ninja Tabi, Mercury's Treads, Boots of Swiftness, Mobility Boots

Replacement Items:
Blade of the Ruined King-
Statikk Shiv, Trinity Force

Spirit Visage-
Banshee's Veil, Maw of Malmortius

Randuin's Omen-
Sunfire Aegis

Blade of the Ruined King: Damage, life steal, attack speed, amazing passive and active. Perfect item for Xin Zhao.
Zephyr: Damage, attack speed, movement speed, cooldown reduction, tenacity. Everything Xin needs to succeed.
Ravenous Hydra: Damage, lifesteal, HP/5, AoE. More Damage, more sustain, and minion clear.
Randuin's Omen: Health, armor, great passive and active.
Spirit Visage: Health, magic Resist, HP/5, cooldown reduction, and 20% increased healing effect (which increases your life steal and healing from Battle Cry.) No brainer item.

Boots:
Usually get Ninja Tabi. If the enemies CC is an annoyance, then buy Mercury's Treads and build Statikk Shiv or Trinity Force to replace the Zephyr. Boots of Swiftness to get more movement speed and reduce slowing effects. Mobility Boots to move faster out of combat.

Flash Ignite is the best combination of summoner spells. Ignite adds more damage and burst, while flash can help you catch up to enemies or escape.

Flash Cleanse if you need to remove any crowd control to catch up or flee from enemies.

Flash Teleport to teleport to wards, minions, and towers to gank and split push easily.

Farming can be difficult for Xin Zhao if you are against a enemy with good poke. In most cases, if you can kill them or get them low enough, they will be scared to even remotely disturb your farming. If you don't pose as a threat and they continually poke you, buy some sustain, whether that be more health potions or life steal. Try to catch them out trying to poke you. They can't trade with Xin's amazing early damage.

Xin Zhao is usually a jungler. He is a jungler because of his great damage and gap closer. Use his natural ability to gank either top or bot, which ever is easier to gank or needs more help.

In teamfights, Xin Zhao is exceptionally great at taking out squishy champions, such as the ADC or APC. Because of his high damage and a disengaging ultimate, you can take the enemy out without the rest of the enemy team attacking you as well.

If your team is losing/bad at teamfighting, split pushing is a viable option with Xin. Ravenous Hydra provides great AoE to clear minion waves, while attack speed provides great turret taking ability.

That's it. All you need to know to spear your way to victory. Thanks for taking the time to read my guide. If you find any mistakes, either grammatically or game-wise, please inform me.