General information
Your Q cooldown starts when you use your first q so if you extend the usage until the end you can surprise the enemy by them not expecting the cooldown to be up so quickly.
Cooldown management is very important. By understanding when your cooldowns are up you can always punish the enemy. Dont be afraid to test the limits of the champion and your own skills through games (though i recommend not ranked as your elo might suffer).
Even though Riven is a champion that is very agressive in the early stages you can fall behind very easily and if you do its hard to get yourself back into the game for 5 minutes or more so bear in mind where the enemy jungler is and be a bit more safe when he is topside.
If you manage to get a lead keep the snowball going and try to extend your lead on yourself and other lanes. Proxy, dive alone or with the jungler if he agrees, get jungle camps, gank other lanes.
Behind
Try not to fall behind as riven as it is very unplayable. You can still proxy or just defend the enemy from pushing but unless they leave lane and give you breathing room to get gold and keep pushing you your only chance to come back is if your team comes for a collapse.
Early game
Riven is a very versatile champion so wining lane or at least coming out with a small advantage is always possible. If the matchup is not very favorable you can try to gain an advantage by roaming. Before minute 5 try to get a good back. As Riven you have all the tools to get all the cs or at least the majority so get a good first back and then try to get platings. Abuse your movement and waveclear you can proxy easily buying you time to move around the map. After level 6 look to all in you have a lot of outplay potential with it. Even if it doesnt lead to a kill they might be forced off the lane which usually will lead to a plate and them missing a wave or 2.
Mid game
Winning or losing you want to go to a sidelane get a push going and since you can do so quickly group up and look for a pick somewhere. Dont be afraid to take towers because you should have decent cdr and able to run if you place a good deep ward. It is completely up to how you want to play it but that is the general rule for midgame.
Late game
Again you want to go to sidelanes get a push going and then look to group. How you play the teamfight is up to you but i generally try to execute someone then just play with my team. You can also peel for the squishies of your team because of your utility and items you should be able to save them and kill whoever is targeting them
