Riven is a high damage dealing champion with good amount of health.In order to play Riven properly u will need to time and plan carefully your spells and combine them with basic attacks.
Riven is the best in short burst attacks and quick escape which will leave your opponent with less then half health, if played properly of course. So lets get started!

You will escape most of the time with your E and Q combo but if it gets tight just hit this baby and u are out of danger.You can also use it for when the enemy has very low health and he needs just that one little strike to finish him of.So you just flash into him and slice.

This is mainly for getting max out of your combo.Your opponent wont be going nowhere that fast and agile with this baby on him.You just hit him and hit and he is dead.Another way to use this spell is to combine it with your Valor i mean escape by that.
When they attack you exhaust them and Valor from them.

Spell i use not so much but it can be useful to finish unreachable enemy.

For Items i go with just so i can get some survivability with good amount of dmg for start.

Next i try to build which will give me survivability i need along with some lifesteal and damage just as crazy farming ability.

So right after i finish my , i go with which will give me everything i need for one healthy dps + on hit slow

After that it is just pure damage: and .

If a game goes on longer than u planed it to u can always sell your dorans blade and buy something tanky

Optional items

First thing i had in mind is it will just give u so much more hp and armor if you are dying to much or tend to be quickly burst down.

Another thing which will help you a lot against heavy tank enemy will be it will penetrate them.

Playing against heavy critical damage is very hard. will help you with that.

Or if u are openminded person just get and have all .

Your main skill will be Broken Wings because it will get you out of trouble more times than u think and it will also deal high amount of damage if used properly.So what i mean by "used properly" is that u must always hit with your basic attack in between your Broken Wings

Another very usefull skill is Ki Burst. That AoE stun is just made for Riven because of a great synergy with her Broken Wings in which u just hit and deal very high amount of damage in that 0.5 seconds of that stun + some more after that.

Valor is your escape spell mostly because of a shield it gives you. It can be also used as engaging spell which works pretty good with your Ki Burst

Skill order for very high Amount of Damage are: Valor+ Ki Burst+ Broken Wings+basic attack+ Broken Wings+basic attack+ Broken Wings+basic and if enemy still lives u can always give him the good old Blade of the Exile or if u need more damage output use your ultimate somewhere in the middle of this order but save your Wind Slash for when they have half or lower HP.

Pros

Great damage dealing combinations
Great for farming
Great for defending turrets
Great mobility
Extra fun

Cons

Squishy on start
Good damage can be done with combinations only
AoE is very limited

Greater mark of Desolation This is obligatory for me in every dps. It just gives u so much more damage on start.

Greater Quintessence of Desolation 10 armor pen.

Greater Seal of Armor Armor from the start.There is nothing more to it.

Greater Glyph of Magic Resist Good MR are basics for every healthy dps