The problem with the advice to use a different password for every site is that it's just too much to remember. The current advice for password management is to use a phrase or sentence that you can remember easily (and exactly) and use that everywhere. The longer the phrase, the more characters a hacker will have to try in order to get it right. Of course the system needs to have a generous limit on the length of the password. For example, I could use
"IloveahandspankingOTKbyabeautifulandstrictwomanbutavoidcanesatallcost" anywhere and feel reasonably confident that it would take years and years for a computer to construct that string of characters.