Howdy there! I see you've found my first guide here on MOBAfire for Riven, The Exile, the most bad *** chick in the League, [and pretty easy on the eyes, eh?]. Thanks for taking the time to read over the build, and I hope this helps you in your matches!

Pretty standard here, nothing out of the ordinary. Riven is a "Melee Caster" character. Meaning most of her damage comes from Spells, while using auto attacks to proc her passive and other on-hit effects such as the slow from or . I use Greater Seal of Alacrity to help in her auto attacks between her combo's.
I take Exhaust and Flash for pretty obvious reasons. You may change these around to your liking.

I start with a for the extra health, attack, and slight life steal. The next item I rush is a for the extra beefyness it gives you.
Riven is very squishy early game. I compensate for this with Phage, and Trinity Force for the extra health and overall usefulness of the item.
The next item is either Boots of Swiftness or a Zeal. You want to be able to stay with your enemies and get your auto attacks between spells. Your passive is your best friend. The Slow and movement speed from your boots, combined with the attack speed runes and Zeal will guarantee you get those passive procs.
I grab a Mid to Late game for the health and passive, giving you some more survivability in the midst of those team fights.
The last two items are solely up to personal preference. Normally I tend to lean more-towards maximum DPS output late game, but if my team is down or I am getting focused a lot I will grab more support/survival items.

By way of skills, I choose to max Ki Burst first, because after all, it's a BURST. The point-blank AOE stun, plus the big damage it does early game is CRUCIAL to dominating your lane opponents. We also want to keep the cool-down pretty low, making it more useful to in, and then back up, giving you amazing early-mid harass. I choose to level later on because I find that having my shield-dash and quick stun to be more useful overall in ganks and escaping.
In late game phases, you should focus on taking out the squishiest person, all the while doing some nice AOE damage with your spells.
Don't spam all spells at once. Use one, auto attack. Use another, auto attack. Mastering your passive is the key to being the best carry on your team.
When team fights start, activate your ultimate to boost your overall damage output and begin to attack whoever is lowest.
REMEMBER, YOUR ULTIMATE'S ACTIVE DOES MORE DAMAGE TO LOWER HEALTH TARGETS. Use this to your advantage to tag that low-health Annie in the back.

That's it, my two-cents on my favorite character in the game to-date. Constructive criticism is always welcomed, and very much appreciated. Remember to vote either way, and leave a tip for next time.
As always;
Enjoy your next match in the LEAGUE... of legends.