Autoattacking in between each Broken Wings will allow the most amount of sustained damage as you consume Runic Blade stacks to deal extra damage.
Since the skill produces three charges, which is exactly her maximum, you may wish to complete it to initiate a fight with her knockback, following up with auto-attacks and her other skills.
Blade of the Exile lasts for 15 seconds so use it at the start of the fight instead of the end of the fight.
While Blade of the Exile is active Riven's attack range with basic attack will increase from 125 to 200 - the highest range of all melee champions.
Using Broken Wings in conjunction with Valor will give you small boosts of mobility as they move you forwards a bit. This is a very efficient way to move around the map, as your moves cost nothing. Broken Wings, however, allows you to click on the mini-map and use it to continue moving, while Valor will cancel your move actions.
Broken Wings can also allow you to chase an enemy and with the knockback may also allow you to get close enough to land your Ki Burst.
Be aware that Wind Slash has a cast time and a travel time as well, so you shouldn't waste it on enemies who are just about to leave its range. Try using smart cast to save precious seconds in aiming the ability.
Wind Slash deals maximum damage to multiple opponents at or below 25% maximum health, therefore use Wind Slash to finish off enemies who are fleeing or deciding to stay despite low health.
Riven is an all-around strong champion in top solo lane due to her ability to avoid ganks with her mobility, her no-mana costs, and her instant cast shield. Play aggressively and use Valor to shield your way through harass.
Riven benefits heavily from cooldown reduction which will allow her to use all her moves more frequently. However, at later levels, Riven is likely to have at least one of her abilities available for use even without cooldown reduction due to prefering to take her time to autoattack between casts and the cooldown of Broken Wings starting even if you delay the later two casts of it, which make the stat less needed then.
Having a way to slow the enemy or speed yourself up is mandatory on Riven.
However, Riven is very good at dealing damage while chasing as Broken Wings moves Riven forward both doing damage and giving her an opportunity to get in basic attacks without losing too much distance. The dash distance is unaffected by Riven's movement speed, so building movement speed items are not as important on Riven as on most other melee champions.
A Frozen Mallet is good for this, since you will be using auto attacks in between abilities to maximize your passive (none of your abilities will otherwise proc the slow). It also gives you health which is a must since Riven is squishy when stunned, sealed, blinded, or otherwise prevented from auto attacking or using her Valor or Broken Wings to escape and/or shield.
Randuin's Omen works very well on Riven as while she may have four ways to dash, they are all short-ranged and Broken Wings loses damage if used fairly far-away from the enemy, and she is still a melee champion that can be damaged by ranged champions without reprisal until she gets close enough. Valor can move Riven close enough to a target to slow them with Randuin's Omen and then walk close enough to have casting Broken Wings move her into melee-range while damaging the target.
Guardian Angel is an excellent one-stop defensive item, and its passive as well both armour and magic resistance can tide Riven for a good while before she may require other defensive items.
Maw of Malmortius is sensible for Riven if she is fearing magic damage - the attack damage is obviously useful on her while the shield and passive works well with Valor and the life steal from The Bloodthirster in helping you survive a bit longer in a close-fight.
Riven does only physical damage, so a Last Whisper is a good item to counter the armor that should be built against you.
Youmuu's Ghostblade should be used after the 2nd hit of Broken Wings or during the last frame of animation of the 3rd strike to avoid losing precious seconds.
Stacking Doran's Blade early game helps due to it's sustainability and AD.
Riven is great for Twisted Treeline. Her strong early game, and mobility with her abilities help her to dominate top lane, as well as give her great ganking ability. She also performs very well in the jungle. After netting a couple of kills early, you should be able to snowball pretty hard.
When you are low on health, do not face Riven as her Wind Slash deals more damage the lower your health is. If you're still squishy and you know she has aqcuired her ultimate, do not linger around with below 25% health even to turret hug, as she can, and will, flank around to kill you with Wind Slash.