Pros and Cons
Yasuo moves fast, has a quick natural cooldown around level 7, and runs on cooldowns only. Also, he builds a natural wind shield against champion attacks as he moves around. His dash attack, sweeping blade, allows him to get into combat quickly. Best of all, his Q attack basically fires off as fast as you can press the button once you have high enough cool down.
Yasuo is flimsy. Super flimsy. He doesn't do well against a long range mid, and he doesn't have enough hit points to sustain against long term combat. You can always build up his health, but I found its best to just do so much damage they can't live long enough to kill you.
Why this Build
Basically, he can't stand up against another player at level 1. However, with a leash, smite, and some health pots, he can clear two mobs and be level 2 in the jungle before anyone else hits level 2. This allows him time to run out and gank or help push near lane for a minute before running back to base to pick up vampiric scepter, then continue back through the jungle to help with mid or top.
Once he hits level 6-7, he should have high enough cool down and damage output, combined with static shiv, to basically walk through minions and monsters as he travels between lanes, keeping up a constant threat on the other team, and his levels.
I've seen a bunch of builds with Silent whisper, and its so useless. Unless you're fighting a bunch of guys with high Armor, then leave that thing. It has it's uses, like fighting Garen, but that's about it.
Also, I've purposely left this guide a bit bare. Yasuo came out yesterday as of the publishing of this guide. I'm sure a better strategy and build guide will be out soon, but this might help you get there!
Start with Red.
Run up to the witch, hit a couple health pots.
Then go to the nearest outer lane.
Gank or push for a minute to get that gold.
If you gank successfully, then go back to base, if not, then hit the little golems and head back to base to get vampiric scepter.
Travel back into the bush, take out wolves.
Hit the wraith, then the golem if you're feeling frisky and not in a rush.
Then run out and gank.
That tends to be the standard for games I've played.
By this time you should have the static shiv and be building toward the Frozen Mallet or one of the other big items. I suggest hitting frozen mallet first because it gives a much needed health boost. You should be able to run out and push lanes and clear towers, and get mobs on your way through. If you've bought boots, then you should be able to move around pretty quick. Not the fastest, but faster than most.
Mobs proved a good place to get your 3rd pip up on Steel Tempest while you're traveling, hit one then run, hit the next and continue on. Remember to E then Q when you strike a group of more than one, before hitting R. Why hit R first? It gets them scared. Drops their health. Then you chase them down repeatedly with E and then Q, and this will finish off the other players.
Around 15-18, you should be frighteningly deadly. damage output is high, you're hard to catch because you dash away, and you can't really be beat. Your Q ability should fire off almost instantly, and it hits multiple targets. Your W ability is there to block ranged weapons, and E to chase down. Don't engage groups by yourself!!! That's a sure way to end up dead. Your strong suit is catching them between lanes, trying to get to the team battle, or escape it.
You're not strong enough for a prolonged fight, though, unless you've got Red. Some of the mobs with High Health and High Damage output may still be able to take you. just make them hurt, then run back out to lane and use trails of minions to harass them with E and Q. Don't be afraid to run into a crowd of minions for some healing with your life steal.
Nifty Tips and Tricks
1. Watch the Youtube video showing off his abilities that Riot has put out. It'll show you all you need to know.
2. You can hit MORE enemies with your Last Breath by dashing into the middle of them, and then using your windblast in conjunction, then hit R. This eliminates some of the issue of having small width of the blast. Your Last Breath ability is a good way to knock down a bunch of health from all of the bad guys mobbed up. Not a good finishing move in Team Fights because it takes too long, your teammates will get the kill usually. ALSO you can target a minion in the middle of them if they seem too spread out.
3. The wind wall is nice, but it's only useful for a moment. Drop it right at the beginning of a team fight to stave off some of those nasty ranged attacks that people like to roll out right at the beginning of team fights.
4. Dash then Q. That's how you chase them down and take them out. If you have the frozen mallet, they shouldn't get away too fast.
5. Be careful that you're pointing where you want to be when you use Q. It goes straight ahead.
6. Leave some minions around to dash away with. Or, stay close to your opponent so you can dash through them.