Google has a page somewhere that explains what they look for in websites and what not to do i.e hide text etc.
When I resdesigned my website I followed these guides, about 4 weeks after i was third.
What I have found though, not sure if its the same in other countries, google maps shows first above all the resaults so most people use this. Which isn't very good when you spend time and money (luckily I did it myself but some people pay £££'s for CEO)
Aaron