Riven has a good tool set, that allows he to put out sustained and heavy damage, but her harassment resistance isn't very good which makes her early game normally fairly horrendous. Unless, of course, we take here entirely out of the lane and make her a jungler where she can get excellent buffs and a good amount of farm. Shooting her through her weak early game into her strong and very strong mid and late games.

Flash: any champion with a knock-back really should have flash for positioning reasons. Riven is no exception. Also, being able to Valor lunge and flash gives her great escape potential.

Smite. U is a jungler...u needs the smites

The typical 1/21/8 defense jungler masteries work well for Riven.

I've also seen 21/0/9 work well. I prefer getting defense as I simply think there are too many "bad" masteries in the offense tree to be worthwhile.

I grab broken wings at level 1. Having 3 abilities at level 1 is better than having 1. Pretty simple.

Level 2 I get my stun for the extra damage.

Level 3 I get the shield. I only makes sense to get all 3 abilities first since they have no cost.

After that I level ki strike when possible.
valor second
and broken wings last
I of course grab my ult at 6/11/16

Why ki strike over valor?

First off AoE stuns are obnoxious, especially in team fights and especially every 6 seconds (with CDR and level 5 of the ability). Secondly, look at the scaling. Ki strike scales by 40 and the shield scales by 30 each level. Additionally, the ki strike benefits from armor penetration while valor does not. Finally, and most importantly, Ki strike clears jungle camps and creep waves quickly while the shield does no inherent damage. This helps Riven's farm tremendously.

Good Rivens WILL level ki strike over valor...Period.

For marks I use attack damage
For seals I use resilience
For glyphs I use flat CDR
For quints I use 1 attack damage and two move speed

Explanation:

Attack Damage over Armor Penetration. Ordinarily, I would go with the armor penetration, however, Riven's shield is the key to her survivability and it scales off attack damage while armor penetration does nothing for it. For this reason, I go with AD runes over any other option.

I use 1 attack damage and 2 move speed in case I don't get a leash. It is possible to do blue or red buff without a leash at level 1 with this setup.

Armor runes are necessary to jungle at low levels.

Flat CDR glyphs will help your damage, survivability, and even your mobility. CDR is important for any champion with no cost to their skills.

I start with cloth armor and potions.
When possible I grab a vamp scepter. This will allow you to sustain in the jungle indefinitely.
I grab boots when possible, upgrading to Ionian boots when possible.
I then start building a brutalizer. After completing the brutalizer
I then pick up a bf sword, upgrading it to a bloodthirster when possible.
I next build a quick silver sash. Focused crowd control will be Riven's worst nightmare as it keeps her from activating her defensive shield in a timely matter and also keeps her from life stealing her health back. The QSS is the perfect answer for this. In my opinion QSS is a core item for Riven.
I next buff up my defensive stats slightly. This is important because, while your shield will now give a substantial amount of free hp. The value of that HP isn't very high unless backed by some defensive stats. Aegis of the legion is a perfect item to fill this purpose. The item also gives a small amount of benefit to allies and boosts AD.
If the game lasts long enough, I next buy an infinity edge. This item will significantly improve your damage and works very well with lifesteal and your passive.
My final item is to upgrade the brutalizer into a ghostblade.

If you have any trouble with hard cc, get a quicksilver sash ASAP.

It's also a good idea to rush if they have more than 1 exhaust or multiple ignites.

If the mages are nuking you, the extra MR will also help a lot...

Unlike many junglers, which are mana dependent,Riven can start anywhere she pleases. It is often a good idea to steal the enemy's golems and then wraiths and then clear your own jungle. This is a risky maneuver since if you get caught, Riven isn't as strong as some other junglers at level 1 (WW, Xin, and Noc will tear apart Riven 1v1 at level 1). But the good news is that Riven can clear these camps easily at level 1 without losing much hp so she can usually escape with the aide of flash. She also has extra mobility in both q and e making her inherently faster than her rivals at the pre-boot stage.

Personally, I like to either start at their golems and go golems, wraiths, wolves, wraiths, golems, (base), red then gank or blue.

Or I start blue and clear the jungle and then return to buy a vamp scepter, then reclear/gank.

Riven is one of the most complex champions to play. Here are some tips to improve your Riven playstyle.

Utilize auto attacks between skills. Try to get one auto attack in between each skill to use your passive stacks. This will GREATLY improve your dps.

The broken wings cooldown begins to reset after the first activation! This is the single most important (and commonly overlooked) thing to remember to improve your dps. Use the first activation on broken wings as your first move every time.

You can use valor to ramp passive stacks before a fight. Once you have a brutalizer and level 5 valor the CD for valor is lower than 4 seconds. This means that valor can be activated again gaining stacks (up to 3) of your passive and you will still have all your cds once you engage the enemy. I call this "valor priming".

Riven has a mini Alistar combo. She is equipped with both a stun and a knock back. Additionally her e (valor) ignores unit collision. To provide additional opportunity for your teammates while focusing a target, hit her once with broken wings to get the cd starting to refresh, then stun the target, q again to get right next to the target, then valor through the target, then use the third activation of q to knock the target back toward your teammates. Now the target has to run past you to get where ever they were originally going and you get a nice set of attacks of opportunity in addition to giving your teammates time to catch up.

Here is how I typically will use my abilities when focusing a single target.

Key: Q= broken wings w=ki burst e=valor r=blade of exile aa=auto attack

R=>E=>AA=>Q=>AA=>W=>AA=>Q=>AA=>E=>AA=>Q=>AA=>R

Bloodthirster and you!
Bloothirster is an exceptionally good item for Riven. Her passive makes her one of the best life steal candidates in the game, rivaled only by Lee Sin. This item allows for permanent presence on the field. Riven needs life steal to be effective. Riven double counts bonus attack damage (a .5 ratio on passive) on auto-attacks while her passive is active. A charged bloodthirster is the most cost effective AD boost in the game.

Ghostblade and you!

The ghostblade is likewise an good purchase for Riven. The ghostblade allows Riven to close on targets without the use of her other skills so that she can combo her skills perfectly on ganks. The active also speeds up your attack animation allowing you to combo more quickly and still use all you augmented auto attacks. Also the armor penetration and cdr will significantly improve her damage and utility.