Riven is an AD champion able to free cast without an energy source and her abilities scale of additional AD damage gained from runes and items. Even though you may want to take advantage of her cost free spells, I ensure you I have tried builds with cool-down reduction and late game damage is terrible.

Riven -
Riven is a mobility champion specialising in combos requiring the user to make decisive actions on weather to take advantage of her passive to deal the maximum damage or spam her combos, Riven is tricky to play but a whole heap of fun.

This is a video from one of my favorite league of legends caster Faro and his first impressions of her - Play Video

Pros -
-ALOT of fun
-Decent farm (her Q and W are AOE)
-Very Strong Early game
-Can get very strong
-agile and mobile meaning easy escapes, moving around and pissing off enemies who use skill shots and kill stealing allies
-No mana or energy pool = no measly mana pots at lvl 1, No recall when oom(IT MEANS OUT OF MANA) and yes faceroll

Cons -
- Squishy (if not runed, mastered and built otherwise)
- Targeted due to squishy nature
- sometimes spells (Broken wings) are useless late game resulting in auto attacks doing more damage
- Bit tricky
- A lot of positioning required
- Required the summoner to be able to know when to string together spells, when to auto attack and when to mash your palm desperately into the top left of you keyboard until your screen goes black and white or when the caller says "PPPPPPPPPPP PENTAKILL!"

I don't know why other guides have this but yes you are free to change rune to you liking for all the guide apart from the jungle as she is dependent on the flat AD runes, the blue/glyphs are the only runes you can change to suit you in the jungle build but the rest are open to change.

for her skill sequence it is the same deal, change to suit the team you are dealing with, get "Ki Burst" more often then valor if your team needs a stun, you can freely change the sequences apart from the jungling build which you should stick by for the first 4 unless otherwise stated. (if I'm an idiot and got the sequence wrong)

The masteries are also open to change mine are only a skeleton for you to build on.

Summoner spell are also free to change w/ masteries but the builds that go into exhaust masteries won't change much as riven doesn't use AP so the AP mastery is useless and if you laning most probably you wont use the smite mastery so i usually leave in smite encase I change the masteries to suit the enemies.

Guides that explain her moves are pointless as they are stated in the guide if you hover you mouse over each move, if you want to know the scaling here is a link to LoL wiki which will also tell you trivia answers - http://leagueoflegends.wikia.com/wiki/Riven_the_Exile (Ctrl+C -> Ctrl+V =Copy->Paste)

The first and the most viable way to play Riven is to jungle with her, she is in fact an amazing jungler in my opinion, her route is simple - The route you should be doing is known as the sustained route or as my friend would like to call it the "pus*y route", this route in no manner is weaker - it is superior as it sustains the jungler allowing him to level faster, gank more often and more freely and will help you level to 6 a lot faster than a jungler doing the "Average" route.

the route goes as follows
1. Wolves
2. Wraiths (Smite the large one)
3. Small Golems
4. Gank or Recall and Buy
5. Blue Buff Golems
6. Wolves
7. Wraiths
8. Small Golems
9. Red/Lizard Buff
10. Gank
(Also feel free to gank anytime during the route and remember to help you solo laner if s/he is struggling)

If you still need any support with your jungle watch this video of stonewall008's jungling with riven he is the renowned "MASTER" jungler, jungling with the likes of Sona and Soraka.This video was made, and performed by stonewall and all credit goes to him.
Play Video
The second build I posted was my homemade Tanky DPS build, this build is a solution to one of her main issues - her squishy-ness. You may vary the build to your taste, such as replacing the banshee's veil with a force of nature or the warmogs armour with a Randuin's Omen. Using this build you will be tough to take down as it will take twice the time to kill you maybe longer and you will most definitely be focus less often.
Obviously adapt the build by not getting the banshee's/FON wit a AD heavy team instead investing in a thornmail or sunfire cape, and same vice versa if the enemy team is AP heavy get a FON and a Banshee's discard the Warmogs or bloodthirster, if the teams are balanced and you need more damage take the bloodthirster.

The last build is the notorious GLASS cannon, I don't recommend this but it does work and is a lot of fun watching someone go to attack you and then you wiping off their entire life bar before they are able to hit you once. but why I don't suggest this is due to the fact Riven is a melee champion meaning she has to get all up in the enemy's faces. This is the guide Faro uses in his first impressions guide.

It's a team game and apart of being a team game is ganking. Obviously you won’t be ganking a lot if you are soloing to or in fact ganking at all, the lane you will most probably gank would be mid (from soloing), try to wait for tour target to over extend. DO NOT USE BROKEN WINGS TO INITIATE as it is your core damage, either flash in or use your valor, use one as the other will be your escape mechanism. when ganking obviously come from the behind, spam your broken wings to knock them back and only just as the y being to run use your broken wings ( if you have your ulti pop that first)

Ganking from jungle

When ganking lanes there are 3 ways to enter the lane
1- from the river, this is the most common and usually used when the target has pushed too far or just enough, as before don't use broken wings to initiate, run in and valor as much as you can then use your broken wings to knock your target back towards your ally, then if they have a cc they would usually use it but if they don't again use your broken wings which is a stupid 0.5sec stun.

2- enter from your tower either your ally has pushed too far or your going for the balls to the walls approach I don't care, if you go in this way you must head into the bushes on the side, then wait for the enemy to push back which they will eventually do, it's pretty simple after that, pop out do as I said before, knock back stun and presto -> instant gold.

3- enter from their tower, go around into their jungle, this is risky and only works in certain lane, DO NOT try it where the entrance is behind the tower, do it if its in front, this will catch the enemy by surprise and will get you a kill unless they're too fast or have a flash, the best way to kill someone who has over extended, stay for too long with low hp and is behind their creeps trying to get some last bit CS or what ever.

NOTES : Try and get your ally to make them pop their flash if they have one
- also if they think something’s up or just wont push get your ally to bait them out by either taking a bit of creep damage or letting them have easy harass on the ally.

yes the items in the builds are also subject to change as I said this is just a basis but I will do my best to explain.

Wriggles in the jungle build is obviously for jungling but in other builds the wriggles is vital to last hitting on minions and provides lane sustainability other than the health pot as u can hit some creeps for some HP. Why AS? well due to the fact that in some cases at late game riven does more damage then stringing together her spells it is viable, I really don't expect you to kill a cho'gath with 1 combo, there will most definitely be at least 6 seconds of auto attacking, and also the damage done by you spell do not count towards lifesteal so auto attacks are important.

Feel free to sell the wriggles late/mid game for the blood thirster.

Read up and I hope you do well with this champion, the best way to learn to play her is not to read my terrible guide but to get out there on LoL and practice with her.

I'm sorry if my guide wasn't up to scratch, I don't really have time to put that many pictures in for the visual learners and this is my first guide which I have actually put effort in, pardon my grammar as English is my second language but I do assume spell check has helped me out quite a bit.

I do hope you enjoy and farewell.

(I will try to add more and update with the upcoming riven(Buff) patch)