I agree with all the above but I'm going to throw a bolt into the gears for a sec.
What I think Google is really focusing on is "why is a new site so gun-ho about getting noticed". All the suggestions above mention getting out of the sandbox fast and getting to your potential clients and getting great rank and blah blah blah.
The question is "WHY are you trying to get out of the sandbox SO FAST?"
Google is looking for sites that have a long term business structure and model. A site that is in it for the long haul. NOT a site that is in it too make some quick cash off adsense. Sell crappy product. Rip off their customers AND overtake legitimate, successful, loyal business in the process.
I understand there are many entrepreneurs out there with limited budgets that need to turn a profit but the best advice I can give is plan ahead (financially and emotionally) for 3 months of no business, load the site up as soon as there is product, dont wait to finish the site but just keep adding product while it's live, spread the word, sing & dance and by the time your finished with the site you'll be out of the sandbox. Rejoice and hopefully good sales will follow.
BTW: SEO the site during the time of sing & dance
It helps ;P
Stomp Stomp Stomp Stomp.....