Google local use many factors to rank local businesses, most are loosely based around the main governing SEO factors.

Firstly have to determine the keywords you want to target (known as categories in local listings). Most businesses have no idea about this and dont take advantage of the categories section in their listing profile. You can use up to 5 keywords, choose them wisely. Just like organic seo, the shorter the keyphrase the more competition you will be up against. The larger your locations population the more comp also, try to target longer tail keyphrases until your citations and ratings have jumped, then shorten the keyphrases.

I heard a great way to put it in laymans terms, a backlink is concidered a vote for a website. The more vote your website has, the higher you will rank. Some peoples votes are trusted and worth more than others. When it comes to local businesses, who better to ask than the master Yoda of local search, the yellow pages directory.

Every business that appears in the printed version also appears in the YP online directory. Usually cost thousands of dollars for a business to place their ad in the YP directory ($40,000 for full page ad in my city), obviously is would be trusted info to Google.

Firstly make sure the local business is actually listed in the online Yellow Pages directory, if not submit it using the exact address that was used in your local Google listing. If the business is listed, make sure it also has their website listed. Most dont. This counts like a vote from the president for your site.

The address listed in the online yellow pages listing works as a citation to confirm the address of the local Google listing.

Lots of cities have multiple yellow page style directories. Submit to all their online directories and always make sure you use the exact same business name, address, phone numbers and website in all. Once you done them, submit the business to all the local online directories, again keeping the info exact. Every country and city has dozens of local business directories online. Start from the most popular and work your way backwards. The big authority directories like DMOZ and YAHOO are also very good for citations and votes.

Who better to rate these local businesses than the citizens that live there. Comments and reviews help a lot with local listing rankings. Get the business to contact their regular customers and ask them to rate and review their listing. Now with easy internet browsing on cellular devices, the business owners can ask their customers to rate and comment on their local business listing, while they are processing their enquiry or transaction.

IMO they are the strongest factors when ranking in local business listings. links and citations from international directories, forums and websites will count for little with local listings. Thats like an American tourist trying to vote in the Australian federal election and expecting the vote to count, not gonna happen, hehe

Other factors that play a part in local listings are keywords in your listting title and domain name.