Easy and 1st: 301 redirects for as long as you can. Negotiate! Medium later: A link somewhere on the page saying, for some period of time: "Dear visitor, were

Easy and 1st: 301 redirects for as long as you can. Negotiate! Medium later: A link somewhere on the page saying, for some period of time: "Dear visitor, were you looking for oldfoo? Click here." Harder and even later: Check the referer to see if they were coming for the old content