From a thread at SEW:

ok get an old domain, something which google crawls, then put a subdomain on it ... newsite.olddomain.com original and copy the site exactly on the sub as it is in the orginal date last modifed to a few months after the domain was first registered ... yer i know that makes all the content look really really old ... lol

Ok add a Link from the real site something like www.newsite.com ( forget about seo anchor text links, these are just to let google in).. now 301 the subdomain to the new site..

Thanks Dave. We all owe you a big one. I think he actually has some other fancy tricks based on this methodology, but I'm glad the cat's out of the bag.