Yasuo can seem like an absolute monster or a complete push over, it all depends on the skill of the player.
Yasuo's vulnerable early game means you want to focus on farming, you should aim to get every single CS available which is more than possible with Yasuo.
Since you have to fly into your enemies face to trade you want to look for opportunities where the enemies minons are gone and when their CC is down or dodgeable. Never engage beyond half way in your lane because you'll either get ganked or end up flying through your enemy and into their tower. Even if you think you can kill them engaging too deep in the lane will often tempt you to either kamikaze for the kill or end up dying with nothing.
Instead, simply outrade your enemy and force them out of lane, while keeping the enemy minions pushing your way.

Generally you want to get shiv first, getting an avarice blade won't help your offensives very much but the extra gold will allow you to get your shiv earlier. Alternatively you could go for zeal first. But if you think you can win all ins early game then go for a pickaxe or B.F sword and rush an early Inf edge. It can make you hit legendary if you do it right.

Getting an early sheen and/or brawlers is great if you can't quite make your I.E yet. Upgrading into a trinity is awesome and will let you experience full movespeed Yasuo, the best Yasuo imo. If the enemy team is too tanky you will have to get a Last Whisper, so the trinity build is best when you become big in the mid-game and everyone's too weak to challenge your damage with armor.

Yasuo's main weakness is his squishiness. But a real Yasuo will know his biggest strength is speed and his ability to dodge any skillshots. The real difference between a noob and a beastly Yasuo is in sweeping blade.
Positioning yourself in minions, carrying a ward to sweeping blade through jungle camps, staying in lanes; this is how you become a beast at Yasuo. Dodge skillshots and your enemy will run out of mana or cooldowns. Dodging is a 100% damage reduction.

Building shiv gives +6% movespeed, trinity gives 20+ when attacking and +8% overall. Furor gives +12% when attacking. With this godlike build you'll have 14% extra movespeed at all times, and about double that when attacking.
You'll be able to chase down or outran many and when you get in the middle of a creep wave the extra speed is exactly what you want to make big plays as Yasuo.

Master the way of the wind and become a true samurai of legend.