For a server I have swap / and /u. /u is where all applications are loaded and where all data is kept. Anything anywhere else that must survive is copied to /u for safekeeping. This way, I can wipe the whole OS and install a later version, or I can format and reinstall after an awful crash or admin error without affecting my data at all or my applications.
For desktops, most applications like to keep user files and configuration stuff in /home/username/*, so I partition swap / and /home.