I have tried this method on one of my sites, that was sandboxed and stood lower than 100th page in SERPs. It seems to have already helped (two weeks) – some pages are already on first page, some pages are in first 10 pages of SERPs. Here is what I’ve made:

I referred to sites description and keywords and picked out a couple of most important. I left all pages relevant these keywords and keyword phrases having deleted the rest. I mean pages that doesn’t correspond general keywords. Usually if you build an ordinary site and care SEO only afterwards, site appears to be half-filled with various dust (that is why my latest sites are thought down to the minutest details: even each sentence and each HTML tag is inspected to correspond my aim.)

Сlean out everything unnecessary. Even “contacts” page can be deleted: you can put your e-mail, address and/or other contacts on your index page, where they’ll be accessible and easy to find. You can target “Contacts” link in your navigation to index page with anhcor on exact row. It just seems that there’s nothing to delete. In fact you can do much. After deleting of all dust, inspect your text content. Try to keep it short and keyword rich. Throw out everything unnecessary, because it is a commercial website, not a novel, where you must give some glamourous idioms and pretentious locutions. Plain text is perspective for SEO purpose and understandable for foringers, which may also visit your website. Probably all of you know that Russian greeting sounds “Zdravsvujte”, but I think that probably nobody will understand it’s synonim “Priverstvuju vas, dobro pozhalovat”. Care everybody, who may visit your site.

After completing your cleaning work, start adding new content. It is much better to add a bit, but daily, than to hold a week and then bring down 100 pages. Regularity is very important.

Using this strategy, you can make good results in recovering a site from sandbox. Good luck!