Yasuo has a very strong laning phase from level 2 to level 7, and once he gets Shiv he really wants to split push. There are a bunch of different Yasuo builds and they have different power curves, so you have to play around them all a little differently.
-> 
is the greediest build. It has a major power trough shortly after you buy Shiv. He also has no sustain with that build order, and no sticking power until quite late in the game.
-> is a slower but more consistent power curve. Has some chasing potential. Stronger early dueling at the cost of a delayed Shiv power spike. Not too much of a power trough here, especially if he goes -> -> 
The new -> 
path is really dangerous. Shiv is a massive power spike, then is immediately amplified and sustained by Phage, which turns into Trinity. Lots and lots of sticking power, really high burst. Once he gets , , and he has 100% crit too. The only issue is that like the -> path, it's expensive.
Okay moving on. If he starts Q, focus on trading. If he starts E, focus on farming safely. As soon as he hits level 2, he out-trades most people in lane until level 3. Pop his shield with autos as opposed to wasting abilities on it. Yasuo's pushing power is really, really strong early on, but he needs to posture aggressively for it. Have your jungler camp him for free ganks if Windwall won't screw your ganks.
The most important thing to work towards early is taking his tower ASAP. Doesn't matter how many times he dies early on. As long as he gets Shiv at a reasonable time and gets to split push shortly afterward, Yasuo's having a good game. Take his tower as early as you possibly can, keep the mid wave shoved to bottle him up, and then focus on monopolising dragon. Yasuo can't really show up to fights early on; he really, really wants to split push and duel someone 1v1 with his Shiv. You want to force 5v4 teamfights by grouping up with your team and forcing them to fight over dragons. Alternatively, you could siege towers if you have an effective comp for that (ie good poke and good tower damage).
Once Yasuo has his second item complete, whatever it may be, he can definitely start showing up to fights. At this point your top priority is to prevent him from gap-closing your carries and dueling them. You can do this in a bunch of different ways:
---You can peel him as he tries to E into your team.
---You can focus him and burst him immediately as he tries to get past your front line.
---You can kite back and deny him knockup synergy with his teammates (you definitely need to kite vs something like Alistar-Yasuo).
---You can have someone super tanky zone and/or duel him for the duration of the fight.
Roundabout this time you guys want to pressuring inhibitors, Barons, or both. If you're behind as a team but can still take 5v4 fights, you're better off pressuring Baron and tricking the Yasuo into split pushing bot.
Alternatively, you can focus on gunning down the Yasuo himself. If he's trying to split push, you can bring your whole team to the lane he's in. It's risky, since you're drawing the attention that he wants. Then again, leaving him to split push and scale is also risky unless you know you can crush the game with mid-game power spikes and effective team play.
Long story short, don't let Yasuo split push for free. Make either him or his team pay for it. Group early, be decisive when moving on the map. Ward a lot, aggressively engage in 5v4's you know you can win. That's all I can think of for now. Cheers!
