Alright, first off this build is what I use personally and I know for absolute certain it works. I have non-stop played riven since she has came out and I have not found a build that has worked better for me.

Obviously these runes will be argued that they are not the best for riven, but I personally think that the suggested runes for Riven were correct. However you can build them differently to your personal needs.http://www.mobafire.com/league-of-legends/edit-build#

As far as masteries go, obviously these are the way to go for riven.

I could spend all day talking about the items and what order to buy them, personally I buy them in that exact order listed above. You CAN buy phage before your ionians boots but I would advise not doing this due to the needed mobility in dominion. If you get a team with alot of stuns or slows / magic users. You will need to go mercury treads in order to do better against them trust me it helps way more than 15% reduced cooldowns.
As for infinity edge, the whole reason behind buying this item Riven uses auto attacks after every ability which i'll explain in major detail on her skill sequences. Once you have infinity edge and trinity force combined together riven will hit much more harder than most melee classes due to the 150% increase after every skill use and increased critical damage.

Alrighty now for the good part.
your skill sequence can be a number of different ways but I personally choose two different style's depending on the champion that I fighting I will list both.
First) E - Auto - W - Auto - Q - auto - Q - auto - Q - auto - E
Second) Q - auto - W - auto - Q - Auto - E ( dash backwards) - Q - auto - auto

As for the First one, This is the more aggressive approach. It keeps your target more disabled from the stun / knock back of your abilities. Keep in mind you do not have to follow this sequence to the letter. Mix things up a bit, the only thing you have to make SURE that you do is auto attack after every ability, or every two (sometimes).

Exhaust - Catch them off the tower ( if they make a mistake ) to deliver a large amount of damage as fast as possible, Or combine both with garrison and exhaust and tower dive them and barely take any damage at all.

Garrison - Personally this spell has one use for me. Tower diving when absolutely needed.