Lulu vs Locke

Cast Help, Pix! (E) on your carry before they trade: they get a shield, and Pix fires along with each of their autos.

Send Pix onto an enemy with Help, Pix! (E), then cast Glitterlance (Q): Pix also fires one from where he is, right on the target.

Save Whimsy (W) for the assassin diving your carry: turned into a critter, they can't attack or cast spells.

Cast Wild Growth (R) on the ally being focused or going all-in: they gain a lot of health, and nearby enemies are knocked into the air, then slowed.

Back instead of staying in lane at low health: Silver Stake (passive) adds damage to his autos that grows with your missing health.

Trade after Ashen Pursuit (E): it's his only instant movement, and its 10-second cooldown only resets if he gets a takedown.

During Soul Ignition (W), only hit him if you can kill him: at the end, he heals back part of the last damage taken, yours included.

Marked by Purgatory (R), stay above its threshold: if you have a heal or a shield, use it, because he seals marked enemies who drop below it.

If the Purgatory (R) artifact lands, hold the area where it fell: by picking it up, Locke raises his execute threshold for each sealed champion, for the rest of the game.