I'm getting ready to move from one dedicated server to another and I want to do this with the minimum amount of downtime. Things I need to move over are.

7 MySQL DB's.
Every Site on the network.
All CGI scripts that control the network.
Need to change the IP of my nameserver.

What's the best way to go around doing this?

It's farily straightforward. Just back-up /home and /var/lib/mysql (or wherever your db's are).

I'd recommend getting the new server set-up and then testing thoroughly to find the inevitable holes before doing away with the old server.

Expect a few issues regardless of planning -- I've helped people do this many a time and I know.

Drew

Get your new server(s) up and running. Customize them the way you want. Start to move sites. Give the customer the possibility to "preview" their sites and the possibility to make changes (scripts, passwords and the like).
If they're satisfied proceed to change the DNS information to point their domains to the new server. = 0 downtime!!!

Well, there are no clients, just my gaming sites, so no one to make un-happy, except for the visitors.