Google Places has a very different algorithm compared to the organic Google Search algorithm. For Google Places, you will be optimizing their one Google Places page to get it to show up in the search results. The two main driving factors are reviews and citations, but I will go over an overview of the rough process you should do for them.
Quick definition of Citation: A listing in a local directory, online yellow pages, etc.
The Process
1. Claim and fill out or have them fill out their Google Places page COMPLETELY. Add descriptions, pictures, videos, EVERYTHING.
2. Have them proactively collecting (hand written) reviews so you can distribute them later on.
3. Go to UBL.org (Universal Business Listing) and purchase just the simple/basic package for them. TIP: Being a pro member of SEOmoz you have a group discount code that will give you great deals and instead of the basic package costing $39, it'll only cost $23. When registering at UBL.org use the code: seomoz2212. That's a great deal for you. The reason for this, is it will give you some nice citations all across the internet over the course of several weeks.
4. Collect the reviews from the client. At this point, you should be a few weeks in with the citations and you will be able to start posting reviews (DON'T EVER PUT THEM ON THE GOOGLE PLACES PAGE).
5. You will start posting reviews on the places with the citations (Yelp, Superpages, InfoUSA, etc.). How you will do this is, first scan your image and then post it to a place like Posterous.
6. Go to one of the places where your business has a citation and register an account, (on behalf of the client) and then post the transcribed review on the site with a link back to the original written review, that you posted on Posterous.
That's rough the process. Now we are posting on the citation locations because Google syndicates that to the Google Places page.
I know this may be a bit confusing, so definitely respond to this with questions and lets keep this discussion going.