Stand beside the minion wave and shove constantly with basic attacks and abilities. This gives Xerath two bad choices, one for positizoning and the other for his abilities.
Positioning
- Stand on your side of the lane and get poked.
- Stand on the opposite side of the lane and not have the range to hit you.
Abilities
- Try to hit you with Arcanopulse and miss last hits
- Try last-hit with Arcanopulse and miss you.
If he stands on your side of the minion wave and tries to hit you with Arcanopulse, then while you won’t be able dodge his ‘pulses or trade back reliably, the wave will soon push to his tower. You’ll lose a little health, but he’ll lose control of the lane.
The following applies to midlane generally. Once the wave reaches the turret, stop pushing it and just go for last-hits while pinging your jungler to gank. Once the wave is near your turret, thin it out enough to freeze it, and Xerath will have lost the lane. If he walks up for last hits, then the jungler will gank him. If he doesn’t, then he’ll miss out on gold and experience.
Even if Xerath has played perfectly by warding one side bush and staying near it while not letting you know which bush he’s warded, his only remaining choice will be to use all his abilities at once, except his stun, to clear the wave, forcing his minions under your turret. Respond by immediately doing the same to keep the wave where it is.
Xerath is now stuck on your side of the lane and can’t do anything about it. He cannot use his stun, or else he cannot play mind games by pretending to ward one bush and then warding and standing beside the opposite one. A flash gank from fog would kill him. Here comes the ‘baiting’ that you might have heard about from higher level players. You need to put the enemy player in a psychological vise.
Every time your abilities are off cooldown, walk in and out of his stun range over and over. If he casts his stun at a distance to try to stop you, then sidestep it because you’re “one step ahead” since you expected him to potentially throw it and were just waiting to see the cast animation. If he waits too long or doesn’t throw it, then just go all-in at your maximum range. Any hard crowd control will interrupt his Arcanopulse, which is where his damage comes from. If your jungler is there, then he will join your all-in.
The reason I mention the stun is that it’s the only ability that he will have up—he needs the others to keep trying to bust the freeze. His only response to you walking up is, under the intense pressure of dying or getting chunked out if he makes any mistake, waiting until just the right range, exactly predicting your movement, and knowing for sure that your jungler isn’t just waiting to flash on him.
You just have to watch and wait for him to mess up.