Xin Zhao is a powerful initiator with both his charge and ultimate dealing damage to all units around him. Try having your team stay spread out until he's used his ultimate.
Xin Zhao relies heavily on his Three Talon Strike for damage and cooldown resets, so preventing him from finishing his combo will have a dramatic effect.
Battle Cry's passive heals Xin Zhao every three attacks, allowing him to sustain himself in lane for a while by autoattacking minion waves and turrets. Doing so for extended periods however will push your lane, so watch out for gank attempts.
Three Talon Strike resets the auto attack timer, so getting one basic attack off, then using the ability will yield a greater DPS.
The attack speed granted by Battle Cry is great for taking down turrets and minion waves, whilst also being extremely effective while jungling.
Audacious Charge does magic damage and slows enemies surrounding the target; you can use that to your advantage by charging a nearby enemy in order to slow another just outside its range. This ability will also pop Banshee's Veil (or similar spell shields) on any of the affected targets which is extremely useful if your team has an incoming area of effect disable.
Bear in mind that if you use this tactic to jump to a priority target with Banshee's Veil, you will want to auto-attack them at least once before using Crescent Sweep in order to apply the Challenge debuff so that they aren't knocked away from you.
To further increase the effectiveness of the initiation, try and aim your attacks specifically at a high value target such as the opposing carry before using Crescent Sweep as this will cause them to be Challenged, reducing their armor, separating them from their teammates and marking them for your allies.
The best time to gank is when the enemy champion has recently used all their escape summoner spells such as Ghost and Flash (or abilities such as Arcane Shift or Rocket Jump).
It is best not to use all your crowd control at once, time each of your crowd control abilities with your ally allowing an easy kill when your enemy gets out of melee range you can then Audacious Charge to ensure your kill.
Crescent Sweep can assist in ganks by knocking enemies back towards your allies, but be sure that you are both in front of them and do not currently have your target Challenged before you do so.
Audacious Charge can be used to escape ganks on some occasions by targeting a minion or a champion along your escape route. Combined with Flash, this can allow Xin Zhao to escape most unfavorable fights. Use it on an enemy across a wall for a clean escape (e.g.: throw ward across small golems wall, then dash to golems, when they flash in or come around, flash is still available for use)
Crescent Sweep can be used to knock enemies away from you when trying to escape.
When attempting a retreat, ensure that your pursuer has not been Challenged first before using Crescent Sweep as otherwise it will have no effect on them.
Battle Cry's and Three Talon Strike can kill a tower very quickly in late game, as long as there are enough minions around to keep it from targeting Xin Zhao. However, if building AP, Xin Zhao's heal lets him sustain from tower attacks even without minions around him.
Xin Zhao has good sustain with Battle Cry. This leads to a relatively safer laning phase than other melee champions. Going for a last hit on a minion at the expense of taking an autoattack is generally more acceptable on Xin Zhao than it is for other melee champions.
Xin Zhao can effectively punish an enemy's wasteful ability usage with Audacious Charge. If the enemy uses their dash or damage spell to farm minions, using Audacious Charge on the enemy will usually lead to a favorable trade.
A good combo for trading is to use the first two procs of Three Talon Strike on minions, saving the third. When an enemy goes to last hit minions, use Audacious Charge and perform an autoattack to knock the enemy upwards. This allows Xin Zhao to get in some free damage.
Audacious Charge can be used to break or at least trigger shields to get their duration running.
Xin Zhao pushes relatively quickly due to the autoattack reset and extra damage from Three Talon Strike and the AoE damage from Audacious Charge. This can be used to quickly push minion waves to the enemy tower, and then open up opportunities for Xin Zhao to roam to mid or bot.
Xin Zhao has a slightly faster turning and autoattack animation than many champions, so using Flash to reposition behind an enemy during an all-out exchange can net you a slight advantage in damage output, which can mean the difference between a kill and a death.
Despite the tooltip, Battle Crydoes interrupt his autoattack animation. Make sure to time it properly so that it activates in-between autoattacks.
Xin Zhao has good sustain with Battle Cry. He can do his first clear of the jungle camps at near full health without the use of potions. Thus, he can save his potions for use in the event that his jungle is invaded.
Starting with and clearing Blue Sentinel will ensure Xin Zhao is near full health and mana for a Level 3 gank if necessary. Starting with and clearing Red Brambleback will instead give Xin Zhao's first gank extra damage and an extra slow at the expense of being low on mana. Getting double buffs will give the best of both worlds, at the expense of longer clear times due to the distance between the two.
It is generally advisable to gank at Level 3 with Xin Zhao to apply pressure on the lanes and help your teammates or yourself snowball. Mid lane or top lane are both decently gankable at Level 3, since those lanes are often played with champions that snowball quite heavily. Bot lane champions will usually be playing it safe, but can also be ganked if the enemy champions overextend. The goal of such a gank is to get a kill. At the very least it will definitely burn Summoner Spells, but ganking for that sole purpose is inefficient.
If there are no gank opportunities at Level 3, then it is generally better to Recall and get the other half of your jungle item rather than continue farming, so that Xin Zhao doesn't fall behind in experience.
Make it a habit of ganking from behind the enemy rather than from the side. Doing so ensures that Xin Zhao can save Audacious Charge for when the enemy uses an escape ability or Flash, since they would have to get past Xin Zhao to get back to the safety of their turret. Ganking from the side gives the enemy too much warning, and puts Xin Zhao in a position where the enemy can more easily get past him.
Crescent Sweep lets Thornmail's passive deal more magic damage which makes Xin Zhao excel in dueling and fights as its active continuously deals more damage because it's damage is based on bonus armor, so if Xin Zhao uses Crescent Sweep in the middle of a teamfight, not only does it do more AoE physical damage, many opponents will not expect the extra AoE magic damage coming to them because it's likely they'll hit you when you go in as they will think it's just his Audacious Charge that does AoE magic damage. Build this against heavy AD carries, it can turn the tide for your team.
For jungle item enchantment, Xin Zhao can get either Warrior or Bloodrazor based on what his team needs. If he needs to be a stronger early game champion because his team comp scales better into the late game, Warrior is usually the better item. If the enemy team has a lot of high health champions he should get Bloodrazor.
Cooldown reduction and attack speed items are doubly effective on Xin Zhao due to the flat CDR on Three Talon Strike. This means that items like Zeal synergize well with him.
Ravenous Hydra is a great item to increase survivability, as the damage and life steal can be enough to keep Xin Zhao alive during heated fights, especially if there are enough minions around for him to feed on.
APXin Zhao can work due to the AP ratio on Battle Cry. With sufficient AP, Xin Zhao can heal himself for tons of HP on every third autoattack. Nashor's Tooth works well with this build due to providing on-hit magic damage that also has synergy with Battle Cry.
Frozen Heart is a great counter to Xin Zhao, since it reduces damage through armor,and reduces his attack speed, which is central to his damage output.
Thornmail is a great alternative, however do remember that he can heal himself through the damage if he has Life steal.
Avoid stacking health without armor as Crescent Sweep deals physical damage based on your current health.
Stay with your allies when fighting Xin Zhao, he can only knock up one target at a time.
Xin Zhao is a melee champion. Harassing him with long range spells/autoattacks when he goes to last hit minions will ensure that he has to pay the price for getting farm.
Punishing Xin Zhao if he uses Audacious Charge to farm minions will generally result in a favorable trade. He has just used a large part of his damage on minions instead of you, and thus has reduced trading damage.
Don't rely heavily on your shield to mitigate Xin Zhao's damage. Xin Zhao has relatively low mana costs and low cooldowns, which he can use to break/trigger your shield duration.
Xin Zhao pushes relatively quickly and thus opens himself up to ganks from your jungler. Ping for help and play passively in order to lure Xin Zhao into overextending.
Pushing the waves toward his turret will force Xin Zhao to farm under it, giving you an opportunity to roam.
Xin Zhao has very safe clears, but does not have very fast clears. Use junglers that can farm faster than Xin Zhao to gain an advantage. Counterjungling Xin Zhao is dangerous since he has high early game damage and clears the jungle at near full health.