Well, Yasuo is a melee Mid Laner, with the hybrid of attack speed, attack damage, movement speed and critical strike chance.

1. Always Stack your Sweeping Blade while jungling, returning to lane or escaping.
2. If your team got a Malphite, Blitzcrank, Janna, Nautilus, Aatrox or other champ who throws in the air, enjoy this moment to strike with your Last Breath in team fights.
3. In the Late Game, you can usa Ghost whenever you want just to gain some Flow while look at a Mobility-Homeguard-Ghost-SweepingBlade supreme god speed.(If you got an allied Karma or Jayce, ask for help.)
4. No matter how much you try, Wind Wall will never block turret shots.
5. Sweeping Blade's dash regenerates Flow too, so use it with no motivation sometimes.
6. if you use Sweeping Blade, and before the dash finishes, you se Steel Tempest, you'll perform a spin, and with the third stack, you'll perform a spin AND throw everyone in the air. use this as a combo. Use your combo as:
Sweeping Blade-Interrupt with three-stacked Steel Tempest-Last Breath-Use basic attacks and block ranged attacks with Wind Wall.

He completely counters Ezreal, Ashe, Draven, Jinx, Janna, Ziggs, Nautilus and a lot of other people, but Nautilus's Depth Charge is underground, so it strikes Yasuo, and Malphite's Unstoppable Force will not be stopped: The champion will not be stopped, just their shots.
He is countered by ANYONE who stuns or stops him, because they stop his Sweeping Blade.No matter how outrageous Gems are, They can stun you. Wind Wall, however, can stop it.

Yasuo in the early game has extremely low health in the early game, but an useful poke. Sometimes call your ADC to gank Mid, so your third stack on Steel Tempest will grant a kill for him, or for you, as you wish.
Late game for Yasuo is really impressive if you got succesfully fed. When you're a fed Yasuo, you can Pentakill dancing. Just like, "Hi! Now you see me, now Pentakill!"
So, you will NEED to buy a Guardian Angel, so you can kill 4, revive and kill the last one, things like this.

GOODBYE!!!