What to exclude from Backups

I'm starting to backup a server running SuSE 9.2, just want to be sure about what to exclude, right now i'm excluding /tmp <-- Temporary data /mnt <-- Other data /proc <-- Dinamicaly generated data /sys <-- Dinamicaly generated data /dev/shm <-- not sure /srv/ftp <-- this will go to another tape Any comments?