Aurelion Sol vs Yasuo

Keep Breath of Light (Q) on the same champion: each second triggers a burst of bonus damage and gives you Stardust.

Farm with Singularity (E): every enemy that dies inside, minions included, gives you Stardust, which permanently strengthens all your abilities.

Cast Astral Flight (W) to escape a gank or to chase: during the flight, Breath of Light (Q) has no cooldown and no channel limit.

Cast Falling Star (R) on several enemies: it stuns them, and each champion hit gives you Stardust to upgrade your next cast into The Skies Descend (R).

Hit him with a cheap attack to trigger the Way of the Wanderer (passive) shield, then start the real trade: otherwise, it absorbs your best damage.

If you have projectiles, save them for after Wind Wall (W): it blocks them all for 4 seconds, on a 25 to 17 second cooldown. Other spells go through it.

Don't stand right behind your minions: each one gives him a target for Sweeping Blade (E), and he gets closer to you with every dash.

Get out of the line of his whirlwind, the third Steel Tempest (Q): without a knock-up, he can't cast Last Breath (R).

Judge his threat by his crit items more than his level: Way of the Wanderer (passive) raises his critical strike chance, so each crit item does more for him.