Strategy and Tactics

Strategy

Jungle Routes

Always get out of base really fast.

Due to Xin Zhao's strong level 2 ganks and not being reliant on Blue, he has various openings.

Path 1: Level 2 Gank
Route: Wraiths -> Red(Smite) -> Gank Top/Mid -> Wolves -> Blue(Smite) -> Shop
Skill Order: Q -> E -> W 

This path attempts to gank very quickly using your extremely strong level 2 kit and the strength of Red Buff. With both Three Talon Strike and Audacious Charge you are able to get kills really easily or force summoners and take them to really low HP as long as your ally follows up.

Path 2: Level 2 Invade

Route: Wolves -> Blue(Smiteless) -> Enemy Red(Smite) -> Gank Top/Bot -> Wraiths -> Golems -> Shop

This path is very aggressive and can payout very heavily, for if the enemy jungler is on their jungle route and is about to or already is doing their Red Buff, then you (still with Smite) can steal the Red Buff and charge in with Audacious Charge and snag a possible first blood while maintaining a dominance in the jungle while also ganking as often as you can. This is a risky path, but if played correctly with cooperation from lanes, this one invasion tip may give your team the hand-up in the early/mid game.

Path 3: Level 3 Gank
Route: Wolves -> Blue -> Red (Smite) -> Gank Top/Mid OR Wraiths -> Red -> Blue(Smite)
Skill Order: W -> Q -> E

This path is similar to the first path where you are aiming to gank very quickly however this gank is much stronger but comes a bit later. The most important thing to note is you need a really strong leash on the first buff you do in order to save Smite without losing much time or HP. Starting at Blue or Red depends on what side you are, and which lane you want to gank.

Path 4: Just Farm
Route: Wolves -> Blue (Smite) -> Wraiths -> Red -> Golems(Smite) -> Wraiths OR Wraiths -> Red(Smite) -> Golems -> Wraiths -> Wolves -> Blue(Smite)
Skill Order: W - > Q -> E -> Q 

This last path just focuses on getting 4 while sustaining HP. You can start on either buff since you aren't dependant on blue buff. You are aiming to just farm till 4 then pressure the map with this route. You want to do this path when you do not expect to be able to kill certain lanes early as it will be pushed to their side or they are just difficult lanes to gank.

Early Game

In the early game, you want to gank lanes whenever possible. As long as you have Q and E, you can gank, having Red Buff helps, but you don't need it. Lanes that have opportunities to gank are lanes that are pushed towards your side, have summoner spells on cooldown, and your laners have sufficient resources (HP, mana, cooldowns) to follow up on your gank. Lanes that need ganks are lanes that are behind either from the lane match up, or assistance or level one fights in the enemies favour. Whenever you do not see an opportunity to gank or have to put a lot of pressure on a certain lane, you should take the opportunity to farm your jungle or go to base and buy if you have money for a big buy (ie. getting Mandreds). You must remember how strong your ganks are, even if the enemy is just the slightest over extended, the huge amount of crowd control and displacement you have is enough to turn it into a kill and force summoners and a blue pill/potions. Look at Tactics section for how to gank efficiently. Counter jungling is a decent choice for Xin Zhao since he has decent crowd control and fighting ability(read the Tactics section for counter jungling info). In addition, if one of your laners require you to hold the lane while they back, do so as well. You also want to control both your blue and red buffs, as well as the enemies. Timing the respawn time or knowing the general respawn time of these buffs are crucial for doing so. Control of Dragon also becomes a big factor and whenever your team has a safe opportunity to do so, you should take it. Oracles is also a really good buy if he snowball with kills.

Mid Game

The mid game is quite similar to the early game. However at this point, you are farming less as your carries may be taking your farm, and you have to be in position to gank and contest Red and Blue buffs, Dragon, and Baron. The same things you do to control those, applies in the mid game, time the respawn of the neutral objectives and buy wards to make the job safer. The power of Oracles persist in the mid game. You are still able to gank very well due to your strong crowd control and high damage, but you do need the help of an ally if you expect to kill a full HP target unless they are really over extended. Xin Zhao is also really good at doing dragon since Three Talon Strike gives him a bit faster of an attack animation and attack reset, as well as having an attack speed buff from his Battle Cry.

Late Game

In the late game, you are a tank, you have to be up front in the fight soaking as much damage as possible, while being as disruptive as possible. However, this does not mean you should be so up front that you are taking free damage from the enemy team. Just stay slightly in front of your carries such that you are able to CC the targets you need to, and be able to dive the carries if the opportunity arise. Baron also becomes the focal point of the game, with most fights taking place around the area. Basically, group with your team and get control of Baron. I don't like Oracles on Xin Zhao late game since you aren't too tanky and you will be diving their carries a lot.

Tactics

Team Fighting

With Xin Zhao you have 2 options in a team fight. You can either tunnel their carries or peel from your carries. Xin Zhao's kit has 3 skills that allow for him to peel as well as dive extremely well. In addition Xin Zhao can also initiate a fight by gaining superior positioning with his ultimate, by either isolating a target, or spliting the enemy team towards your team and away from your team at the same time.

Counter Jungling

Xin Zhao is good at killing a single target quickly, making him a decent counter jungler. However, he has little to no ability to escape in his kit. The only ability to helps to him escape well is his ultimate, and that is not a skill you want to use for the sake of a Blue Wraith. When counter jungling, you must be aware of where the enemy jungler was last seen, and the status of your lanes. If creep waves is pushed towards your side, it is more likely you can be caught in the enemy jungle. You should almost never attempt to counter jungle if you do not have an idea where the enemy jungler is and if there is a ward where you walk through to get into their jungle. 

Tips and Tricks

How To Jungle Efficiently

Start camps by using W then attack, then use Q to get an auto attack reset and just keep attacking the creep and repeat this. If you have mana to spare, you can use E before W to jungle a bit faster. No special tips/tricks for jungling with Xin Zhao, really straight forward.

How To Gank Efficiently

Ganking Without Crescent Sweep

When ganking without your ultimate you want to initiate immediately with Audacious Charge followed by activating Battle Cry. Follow up with auto attacking then using Three Talon Strike for an auto attack reset then constantly pummel the enemy to get the knock up. If you need to use Summoner Spells to get the third hit in and they are low enough for you and your ally to kill, do it.

However, if you are able to come in from a really good angle behind them, begin with using Three Talon Strike and Battle Cry and save your Audacious Charge for until after they Flash or get out of melee range.

Ganking With Crescent Sweep

Once you have your ultimate, you want to get behind then and use Crescent Sweep to knock the target(s) into your team making it more difficult for them to get away then walking up and hit them with Q and W activated. Follow up with Audacious Charge when they get out of range and use Q, W, E whenever it is up. If you are unable to walk in from behind them, you can use Flash or use Audacious Charge on a minion to get a good position and try to hit them with the AoE of Audacious Charge while you are at it.

Synergies and Counters

Synergies

Xin Zhao works well with champions that have crowd control so he can combo his Three Talon Strike without them getting anyway. Examples of such are Ryze, Renekton etc. In addition, since Xin Zhao is not really tanky unless fed or gets a really good ultimate off, having another tank in your team is really good, either in top or bottom, or even tanky mids like Swain.

Counterpicks - Jungle

These counte picks just make ganking with Xin Zhao very difficult. Nunu's snow ball will make it very difficult for you to combo your Three Talon Strike properly due to the immense attack and movement speed slow. Alistar and Singed on the other hand will just knock/throw you away after you use Audacious Charge.