What's the best way to pull out of the Google sandbox? Is building quality backlinks from high PR pages really the only thing that's going to get my website back in the race?
Check your site again. do the complete analysis. change the site design. change the content. Don't do keyword stuffing. check if any bad neighbourhoods links(viagra,condoms,sex,terrorists links, or any malware links) is present in your site. Check your all baclinks. remove your links from any banned sites or any adult site. Change the meta tags. After doing these all things send your site via google webmasters tools to Google for reconsideration. Google checks it again if your site is following the guidelines of google then it will remove your site from sandbox.
What madhav said + make sure to gain authority backlinks instead of low quality ones. Look for the PR of the sites that you are getting the links from. The easiest would be to leverage web 2.0 properties such as Squidoo and Hubpages
One single strategy to pull your site out of the Sandbox does not exist, it requires a number of things to increase your chances..
Backlinks, backlinks and backlinks. Keep building and get some .edu or .gov would help as well for the same keyword you wish to target. Don't vary your anchor text.
Just wait until you site gets out of sandbox then after that, start link building again. Improve too your site as well.