The Core

Ensure you have reviews on any of the sites google scrapes for ratings (preferably several) and/or via google reviews direct.

They may then start to associate your ads with your reviews profile automatically - easiest way to ensure this is upload a product feed, claim your places page, and associate your ad account with your product feed. If all those accounts are linked (not necessary that they're all on the one account, just make sure they're linked in the appropriate boxes in product/ads etc) then the ratings will start appearing.

You can rdf review ratings and submit them directly to product if they don't seem to be allocating you a rating. Afaik the stars which show relate to the company profile not to an individual product rating.

Note they say somewhere that they only appear if ratings are above a certain level - I haven't tested this, I think it's true though because they want the click through. Don't believe star rating currently impacts your CPC directly but it would make sense if they work it into quality score eventually.

that would make sense, although I don't really know - I often get the feeling these things are reliant on someone in Dublin making the connection manually to be honest - might also be worth marking up the reviews rating with an rdf tag as a belt and braces - I'm about to try this to try and force stars in the SERPs for one site and it doesn't look too onerous.

http://www.google.com/support/webmasters/bin/answer.py?answer=146645

most sites *except* FeeFo, I believe.

Can you tell I have a client uses Feefo? 

yeah, you'd only be a total saddo if you had heard of it