It's easier to land Arcanopulse on an enemy when they're moving toward or away from you, rather than side to side.
Eye of Destruction will make landing Arcanopulse easier as the target will be slowed.
If you stun an enemy with Shocking Orb, follow up with a guaranteed center hit on Eye of Destruction.
Xerath's range can be intimidating, but most champions who close distance with him can trade favorably.
Xerath takes a long time to engage Rite of the Arcane. Watch for his spellcast animation and start dodging.
Banshee's Veil will make it much harder for Xerath to land Shocking Orb on you.