There are currently 2 different local ranking algos, but the one that's most common right now is the 'blended' algo.
With the blended algo there are in my estimation about 300 ranking factors. The most important of which are regular organic ranking factors.
Yes you need citations and reviews help some. And you also need a well optimized Google+ Local page that is free of violations.
(Google is penalizing non-compliant listings in a variety of ways which includes more aggressive ranking penalties.)
So again you need to have everything above well optimized, but what moves the needle most is doing an exceptional job of LOCALIZED on-site SEO.
David Mihm's Local Ranking Factors is pretty much considered the bible for SEO, so if you want to learn more I'd study this doc in detail.
What else do you guys think is important?