Well I'd like to first start off by letting you know this is my first time making a guide and would appreciate any tips or changes I should make to this guide within this. Secondly, try to avoid insulting me on my opinion of the item build as much as possible as it is of course, an opinion that I am sharing to the rest of you.
I baught Riven about the second day she came out and ever since, I've been trying to make a build for her that I thought would fit best as a melee dps, but still had some survivability to save me from my stupid actions. It was difficult to decide on the items to exactly buy and when because Riv is a tanky/dps. Her CDs are long and she attacks so slow, not to mention the lack of range she has with her spells(they took the broken sword too seriously). After much debating and making multiple builds, I finally came to the conclusion of this. I would love to hear your comments on what you think and anything that could benefit to this guide.

(9/21/11): Guide Published!

Broken Wings Important!

Always Auto attack in between Broken Wing's charges to use your passive to its best potential. If your able to get more then one in between then go for it. but Three is pushing it. Only time you should not worry about auto attack in between is when in team fight and your all burning one or two people because you want that last hit!(:

Blade of the Exile

When using Wind Slash, The lower health your enemy is, the more damage this does. So wait untill they have about 1/5 of hp left. 1/4 for late game.

Attack damage

im sure many of you will look at the hp when loading this page and then backout because its 4k, that means tank build? Well for those of you who dont do that. Keep in mind that the attack damage is not added from Atma's Impaler to the stats. This is very important because the build itself already has a lot of damage, adding 2% of your health into damage is a big phat boost.

Pros

Hits hard
Great at harrassing
Can use abilities to run away
Tanky
Very universal on how you want to play her.

Cons

Can be squishy till built HP
Slow hitting
Abilities can put you in wrong spot(near turret)
Small melee range

Exhaust

This slow is great to catch your enemies from getting away from your wrath and a nice boost over your opponent. You can always trade this out for Ignite but I prefer not to.

Flash

A problem I have sometimes is catching a runner or getting away from someone. This is a must and saves me a lot. As well as gettin that kill running from me.

I always try to build broken wings first but I keep Ki burst kept up because of its nice damage early game. If you have trouble staying alive. Go defensive and do Broken Wings once at level one, then Build KI Burst all the way. After that build Valor to max. No matter what, always do your ult > anything else.

Mark of Strength:
I chose this rune because all Riv stacks is attack damage. She does not have a lot in beginning so its important to build as much as you can, as fast as you can. These runes are a must.

Seal of Resilience:
In early game, Riven is pretty soft and can really get beat to death in a counter-harrass. These are great to medigate the damage and can really make a difference. These runes are very helpful when it comes to laning vs two others.

Glyph of Focus:
These runes make the greatest difference for Riven because her abilites have such a long cooldown. Riven is already crippled with the lack of attack speed and makes her very dependent on these, Not only will you have great burst, but with reduced cooldown on spells, you can sustain that damage output. The only other runes I would recommend besides these is Glyph of Shielding for magic resist. Other then that, Focus is a must.

Doran's Blade

I have tried to start my build off with long sword and a health pot in the past and any other item you could possibly think of and nothing can give what Doran's Blade does. It has that little health boost to put you above, that damage in the beginning you need just like long sword, and the lifesteal can go a long way when you cant or dont want to leave your lane to regen your hp up, slowly.

Boots of Speed

This is just common sense, you need to be able to catch up to your opponents just as fast as you need to get away from them. They are also cheap which makes it great to grab early game. I do not believe you should buy these before Doran's Blade so please dont.

Ruby Crystal

The biggest problem I have early game is staying alive after attempting to harrass, you have to get really close to your enemy to hit them with Riven's abilities and this little health boost gives you enough to look intimidating with health and allow you to live in those early on fights because she really is squishy and vulnerable early game as much as she hits hard.

Mercury's Treads

By the time you get to buying these your enemies have some sort of CC to stop you and the tenacity makes a nice difference. If Riven gets CC'ed too long, her broken wings Cd starts before you used its three charges and can cause a problem. Also the magic resist is a great benefit since you are pretty squishy early game.

Phage

This item is great because it gives you exactly what you need. The health to stay alive on your harrassing, the attack damage which is all Riven builds, and a slow to catch up with those runners and get the kill. I have such a problem with catching up to people once they run from me and dont want to use my spells, yet when im running I have no trouble getting away. That slow is a great benefit and makes a difference when getting the kill before you reach the turret.

The Brutalizer

This item builds into Youmuu's Ghostblade and is just better to buy vs avarice blade because it gives you AD and some more CD reduction.

Youmuu's Ghostblade

I buy this early/mid game because it gives that little attack speed and movement speed I need that Riven lacks. The 60 sec. Cooldown on it is great and makes burst damage all that better as well as a nice tool when running away. This item has a lot of benefit and is just a great item.

B. F. Sword or Giant's Belt

That dreadful item everyone hates to wait to buy. Once I have enough health from my phage and attack damage to rest on, I start to save for B.F. because it jus blows up my damage. If the game isnt going so well and your dying too fast, go ahead and buy Giants belt before it.

Frozen Mallet

Just a higher version of phage and cheap to buy in my opinion mid/late game. The slower your enemy can run, the better chance of you getting a kill and avoiding turret feeding.

The Bloodthirster

Now I buy BT over Infinity Edge or BlackCleaver because you have already built the health to stay alive and take a hit. If you stay alive and in the long run, the Bloodthirster is so much better then I.E. and cleaver because at it adds more damage and lifesteal each kill. At max potential it gives 100 attack damage and 55% lifesteal. Thats just incredible for Riven since all she wants is AD. If you get killing blow on minions it even builds up, just so much slower.

Regrowth Pendant

That nice boost of health regen which is cheap. Also goes into your final item built, Warmogs.

Atma's Impaler

Im always so excited to finally buy this item because all that hp building like a tank finally pays off. 2% of your MAX hp is added to your attack damage. You already have a tank amount of health so once this is thrown into the mix, your AD just effing skyrockets.

Warmog's Armor

I buy this because now that you have atma's, all that hp = AD so its like a double awesome benefit. this is a no brainer and self explainable. Health to live which ends up being turned into damage, the most important stat for Riven? Your invincible by the time you reach this.

BEWARE

Can be KS'ed pretty easily, learn to time spells for final blow. But by mid/late game you hit like a truck so wont have to worry bout it too much.

having trouble centering some stuff for title. Like Pros and Cons and making the word important big and red, not jus one or other lol. Also putting images next to the item names. First guide. help(: Thank you so much. I hope this works out great for all of you. Please vote and leave comments. I appreciate your responses.