Close Gap> E,W,Q
Finisher Combo> W,Normal Attacks,E,Q,R (with Frozen Malat put the norm attacks in for extra damage)

Riven is a good initiator of team fights. To do this wait for either enemy team to group up in one relatively close spot or for enemy champion to over extend then use your E as a gap closer and immediately use your W to stun which allows fellow teammates to arrive in the fight as you spam your Qs on enemy champions. By the time your teammates are there you are already on your last Q which will airborne enemy champions allowing your team to also get an extra jump on damage as well.

Its very important with Riven to know when to use your W and Q in teamfights. Knowing when to use these skills and when to refrain from use and save them is an important thing and will help save your teammates as well as your own life. You should try to save these CC moves to interrupt high damage output moves such as Katarina's, Nunu's ultimate or even Fiddlesticks as he prepares for his ultimate. Just by saving one of those two moves you can shutdown these high damage area ultimates and make winning your teamfights a walk in the park.

I recommend the summonor spells flash and ghost because Riven is very good at chasing fleeing champions with ease and killing you even just slowing them down for teammates to assist her. Also with the combination of these spells it allows Riven to exit bad situations such as mistimed and placed teamfights with ease to insure that their will be no ace of your team.