if you read the stuff by danny sullivan (who i suppose we can all agree is an SEO expert), there's not a lot of concrete stuff there.
He very rarely says "do this and you will jump up the SERPS". its all best guesses.
look at his most recent quote about penguin -- "Is Penguin a site-wide penalty like Panda or page-specific? ...Given that Panda has site-wide impacts, I think it's a fair assumption that Penguin works the same."
A fair assumption? So even he hasn't got a clue!
Here is his 4-step "expert" advice...
-- Clean up on-page spam you know you've done
-- Clean up bad links you know you're been involved with, as best you can
-- Wait for news of a future Penguin Update and see if you recover after it happens
-- If it doesn't, try further cleaning or consider starting over with a fresh site
so, to summarise... clean up spammy stuff and see what happens. if it doesn't do anything then try doing it again or just give up and start again.
im not knocking danny sullivan, because i read all his stuff. but that is the truth about SEO experts... if someone as clued up as him doesn't have anything concrete to tell you then no one does.
leaving the obvious stuff aside (like adding <h1>s, good titles, and attracting trustworthy backlinks, blah blah blah) its all best guesses.