Newness, exact keyword domain and rapid backlink building (only in 100 or so directories) seems to do the trick.
I disagree - the reason I know this is within my niche I have two sites that are ranking very high for a single keyword that haven't been touched for 5years! ( they are not my sites)
Looking at the serps they are a mess and I believe if you keep content level high and building solid links your site will recover ...in time! as G will not want to leave the rubbish thats current in place