This generally excellent article covers issues to address when redesigning a website, in regards to Search Engine Optimizatiion:
It does omit how to do redirects so you don’t lose your existing rankings – a subject which is thoroughly covered in Google Webmaster material (see: 301 redirects).
Usually people pay attention to NONE of these factors, because neither the client nor the designer understands SEO.
At best that is a big waster of time and money since a lot of this takes no or little extra effort.
Done later it can be a major pain, even requiring a complete additional redo or rebuild of the site.
