EDIT 11/27/11 * Updated Masteries (finally) *
EDIT 10/1/11 * Updated skill sequence a bit *
EDIT 9/16/11 * zomg graphics! tweaked items a tad *

Special shout out to:

Zedera

for all of his support! Check him out!

Riven just came out and she's really fun to play. After a couple of matches with her, I found something that works pretty well.

Most of them speak for themselves:

Marks: Greater Mark of Desolation Armor penetration for AD champion

Seals: Greater Seal of Armor Flat armor bonus because Riven starts off kinda squishy and this will greatly improve survivability

Glyphs: Greater Glyph of Scaling Magic Resist Flat magic resist or you can do magic resist per level. Either work and will give Riven the magic resist that is desperately needed.

Quintessence: Greater Quintessence of Health I do health quints so you can better harass early game

21/9

I went for a more full on offense mastery set.

Offense Tree: grab as much AD and armor pen as you can. I did grab the CD reduction as well instead of any ability power.

Defense Tree: I opted for health regen here. Before a match, make sure you tailor the tree for either added magic resist or added armor.

The Good

Exhaust Is what I recommend. Instead of trying to use Ghost to catch up, simply slow enemy champs down and easily catch up with Valor and stun with Ki Burst.

Flash Riven is in the thick of a fight, so escape options are limited to Flash and Valor.

The Meh

Teleport is an ok option, but not recommended. With Broken Wings and Valor you can easily get back into your lane quickly. The only reason I would recommend it is if you need to jump to the other side of the map quickly, but I can't see someone planning that ahead of time.

Heal is also an ok option, but also not recommended. You have two Doran's Blades and shouldn't really need Heal if you're careful enough.

Ignite is probably at the top of the "meh" list because you can add some extra harass to your laning.

The Bad

Ghost is not a good choice. Valor gives you no minion collision and you can easily escape with other tactics. Need to catch an enemy? Grab red lizard buff, activate Ghostblade, or Flash and Ki Burst.

Most everything else.

Maxing Broken Wings first is a no brainer. The rest of it is to be determined by gameplay.

Laning

If you are up against squishy opponents, grab Valor first so that you can dash in and do some damage. If you are constantly being harassed, Valor may give you some additional armor, but Ki Burst gives you .5 stun so that you can get away.

Farming

I tend to start maxing out Ki Burst before Valor, mainly because you can farm really well with the damage output from Broken Wings and then Ki Burst. Both give AOE damage and you can quickly get through a large amount of minions or tight grouped monsters in the jungle (Wraiths).

When looking to jump into a fight my skill sequence usually looks like:

Valor > Broken Wings > Auto Attack > Ki Shout > Broken Wings > Auto Attack > Broken Wings or Valor (depending on the situation). Broken Wings for more damage or Valor if trying to kite and run away or wait for a team mate.

I didn't post an auto attack between Ki-Shout and Broken Wings here. This isn't the most efficient as many will say. This is just pre level 6 and is meant for quickly dashing in (Valor), dealing a bit of damage, and using Broken Wings or Valor to get out. Harass until you decide to go for a kill (usually with the support of your teammate).

Once you have Blade of the Exile, always open with it before a team fight. The reformed blade gives you extra attack damage and does more damage the lower you're enemies health is. About half way through the skill sequence, or when Blade of the Exile is almost done, you can Valor out to get some distance and use Wind Scar for maximum effect.

Here is a skill sequence for level 6+ and yields the most damage. (Will vary depending on what you decide to level up first/hit with 3 Broken Wings, etc)
Blade of the Exile > Valor > Broken Wings > Auto Attack > Broken Wings > Auto Attack > Ki Burst > Auto Attack > Broken Wings > Auto Attack > Blade of the Exile

This is efficient because both Broken Wings and Ki Burst reset your auto attack.

When looking to catch an enemy champ, you should look to delay them the most that you can. If you can get your timing right:

Broken Wings > auto (you might be too far for auto, it just depends) > Valor (to catch up) > Ki Burst (to quickly stun) > auto > immediately go for Broken Wings > wait for a bit (maybe land an auto) > Valor to get right on top of them or in front of them > Broken Wings a third time. The knock back (if done right) should give you an extra one or two auto attacks or give you time for another Ki Burst which in turn gives you time to land some more blows.

This is a big one.

Many people have opted for Trinity Force (for Sheen of course) and it was one of the first things that I tried out when I first bought Riven. Yes, it procs with Broken Wings, BUT it doesn't really help a lot and it's a really expensive item. If you buy it in game, you'll see what I mean when I say you wish you had a different item. Biggest thing here: save your money for a B.F. Sword.

Opening

This is HUGE for Riven and it took me quite a while to figure something that works really well to carry you into mid game. Doran's Blade > Boots > Doran's Blade. This is in here, because it WORKS.** Some will opt for Wriggle's Lantern, which can be a viable option if you need some extra armor, but the double Doran's Blades will give you health and life steal that is needed for sustainability and damage. Out of all of my openings, this seems to work the best.

**Edit: If you feel like you don't need the speed (fighting slow champs/great cc partner/something) build two Doran's Blades before you grab Boots. This yielded great results for me and give you a bit of a change up if you're feeling up for it/you're good enough with Riven.

Mid Game

Boots of Lucidity Boots of Lucidity for cooldown reduction, which is key for Riven so that you can spam your Broken Wings. In essence, there are two things that you can do with Riven, either Boots of Swiftness or Ionian Boots of Lucidity. Why? Aren't Mercury's Treads a great option? Yes and no. Yes because tenacity, BUT when you play Riven for a while you'll start to dash in and out of combat with Valor and escape with Valor and Broken Wings. I only even mention Boots of Swiftness because they might help catch champions, but using Exhaust is much more effective, and you can grab the cooldown from Ionian Boots of Lucidity which is a more viable option.

Infinity Edge. This should rush for a B.F. Sword as soon as you can and farm for Infinity Edge. Once you do this, in combination with your two Doran's Blade, you will do a great deal of damage. You should be able to easily farm for a B. F. Sword and complete Infinity Edge by around 15 min or earlier depending on your ability to harass your enemy.

The Brutalizer. I love this item on Riven because it gives you both attack damage and cooldown reduction. Both of which are perfect for her. Mid game, this will give you extra cooldown so you can continue to smash with your Infnity Edge.

The Bloodthirster. A must have for AD champs. Some may want to go for Black Cleaver, but I don't feel that the attack speed really helps as Broken Wings will proc with AD and is the skill you will use to cause the most damage.

Late Game

These items are kind of up in the air. I chose

Frozen Mallet because it gives you 700 health (which should put you up around 2.8k health), a bit of AD, and slows your target at you hit so that you don't have to waste Exhaust.

Also up in the air:

Youmuu's Ghostblade
and
Phantom Dancer. These two items will give you some extra attack speed, but like I said earlier, attack speed isn't the key. I buy these items for the active on Youmuu's Ghostblade and the extra movement and crit from Phantom Dancer. Usually I don't even have time to finish either of these because the game is over.

Other options:
If you need more survivability, some will opt for
Banshee's Veil. It's an all around good item as long as you don't mind wasting the extra mana.

Force of Nature might be a better option for magic resist, depending on who you're fighting and if you really need the spell shield.

Randuin's Omen is a great late game defense if you have the money and want to build it instead of attack speed. The only reason why I don't build it later is because of the cost and because my survivability is taken by Frozen Mallet, which I feel is a better option.

Hexdrinker. I feel like this is a big controversy because a lot of people want to build it. Yes, you get the attack speed and you grab great survivability early game against spell nukes, but I feel that it takes away from more important items early/mid game like Infinity Edge. If you want to built it instead of The Brutalizer, you might have more luck with it than I did, but if you have a team to back you up and learn when to fight and when to run, you should do a lot better without it.

Warmog's Armor
and
Guardian Angel are two items you can supplement late game if you need additional survivability. I've seen Riven with Guardian Angel, and she does decent especially if you're fighting against champs like Tryndamere. Warmog's Armor is a toss up for me because while 3k+ health is nice, I tend to opt for the more dangerous AD and AS parts of Riven. Once you get used to her and learn how to play her well, you can decide if you want to buy either of these items.

Cloak and Dagger. This was brought to my attention and I felt I shouldn't leave it out. It is an interesting choice and it's a cheaper alternative to Phantom Dancer. I think I would only consider it if I was low on money as Ghostblade's active has allowed me to grab a kill in more than once situation. In my next couple of games I will try Cloak and Dagger out, but like I said, I'm rarely able to finish my build because the game ends, haha. Building Cloak and Dagger might be a viable option with The Brutalizer, but I will test it out in some games and post back later.

Pros:

Fantastic early/mid game
Great harass
Great survivability for maximum damage

Cons:

Expensive build
Relies on teammates (doesn't everyone?)
Low magic resist/armor
Hard to play

Riven is a fantastic character once you learn how to play her right. With team help, first blood is easily achievable depending on who you're fighting. I'll make more item builds in time to account for different situations, but this is my main standard build and have a lot of great games using it.

Please post comments/suggested changes and be sure to vote! :D