You want to go in at lvl 3 and e q and the moment the target is airborne w, the target can't dodge the w while airborne and is then slowed. If the enemy hugs the tower you should go roaming and try to kill the other enemies. Remember Xin zhaos primary role is a jungler (although I think he is stronger in the midlane) so his ganks are very good and he is one of the strongest early game duelists.

During the early game your w is your main source of damage that's why you should max it first.

Xin Zhaos w is an excellent Zoning ability!