Riven is a champion that basics on AD. 0 ability power, 0 mana, 0 magic damage. Simple, he?

DO NOT PLAY HER AS JUNGLER. SRSLY. SHE IS NOT A CHAMP CREATED TO JUNGLE. IT MAKES RAINBOWS CRY.

Now now now, to say AD champion is not enough. Most important things to max on her are:
- Cooldown reduction (First thing you do is reach max cooldown reduction. Thanks to it, you can spam your Q and E, what gives you 4 dashes! It's making almost same distance as flash, even if not farer! It also helps you to reach enemies, stun them, then reach them again, stun again.. And of course, your ulti is very important. When you'll use ulti, with 3 stacks on passive... hohoho!)
- Attack damage (Err yeah, coz she's AD champ..)
- Attack speed (Not too much, a lil more than 1.000 is enough. How faster you attack, how faster you make your crits, etc.. important.)
- Critical chance & strike (Yes, beacuse she's crit champ too! Her crits, with her passive are so powerful. When you'll have Infinity Edge and Youmuu's ghostblade, on 18 lvl it's surely enough crit chance. So after getting those two items and having 18 lvl, remember to advance your critical strike, with items like Phantom Dancer.)
- Lifesteal (yeah, lifesteal for ad champs is always needed... And while she's having such a good dmg and atk speed.. sure Bloodthrister should be enough.)

Yeah, 21/0/9. But w-w-wait...
"Y U MAX OFFENSE AND NO CHOOSE FINAL MASTERY?"
Beacuse she doesn't need it. It gives only 4% attack damage and magic damage, which she doesn't have. I preffer to choose Greed, fastar goldah.

UPDATE 19 SEPTEMBER 2011

After thinking, you can choose final mastery in Offence too. 4$ more damage is not very much, but it may be more useful than 1gp10s. I dunno.

Greater mark of Desolation - Armor penetration. Helps alot in early, and useful whole game too.
Greater seal of Viality - +175 hp at 18. Beacuse she's kinda squishy, and she needs every life point.
Greater gylph of Shielding - + 24 magic resist at 18. Here you can change runes, beacuse I'm not sure about this, but it helps a lil against mages.
Greater Quintessence of Furor - +13% Crit dmg = +100% awesomenes

"DO IT, ******!"

Yes, beacuse she is awesome farmer. Even on 1st level, she can easily farm. So if you're afraid of enemies, or just have a free second, go farm alot.

Of course max Q, but don't forget to have all 3 skills at 3 lvl too. They make incredible combo. And then max Q. And after maxed Q, max e. Then W.

Enemy too far?
Qx3 + E
Got him?
W + R
He's still running away?
R (wind slash)
STILL ALIVE?
Q + E + W +FD9780728YAS7DOGY
Ran away?
Call Karthus then. Trolololo

Yes, I think it's not big problem, if your enemies aren't harrasing you too hard.

NO

So, I think I said all important things. Any questions? Ask in commentary. I'll respond so fast as I can.

http://www.youtube.com/watch?v=zD0YMpGfUt8

Riven getting her quadra kill on bots. Of course this build which you can see there isn't serious.