Riven is by far one of my favorite characters to play. She's excellent in combat or team support, and can switch between a very powerful off tank, or a strong damage carry.

Runes are based around penetration, health, and survival. All around offtank, and I prefer .5% health runes, as they scale amaziningly with Atama's

For Riven's masteries, it's basically the same as any AD carry, with a bit more defense thrown into the mix. I play full offense until 21, then carry over into the defense set for health and armor, trying to equal out magic resist vs armor.

Offtank item set, building around health and damage. Rotate into the health items moreso if you need it, and swap out to more damage to gain an advantage if the other team is having trouble.