[Zope] Best way to upgrade an existing Zope installation?

Hi there Maybe this has been answered a million times, but I can't find it. What is (generally) the best way to upgrade an existing Zope installation? (Including products, etc.) Must I export/import everthing, can I just copy the data.fs file or install the new Zope right over the old one (and then recopying the data file)? Thanks Etienne Tel: (012) 348 4586 Cel: 082 442 8981 Fax: (012) 361 8355