With 40 gigs I would at least make quite some room in /home and /usr/. /home is where stuff like your documents and downloads are gonna go so you do not want to run out of space there. /usr is where you software will mainly be so if you plan on installing quite some programs make enough room. /swap used to be set to about 2 times your ram, but I read that going over 1 gig is useless. /var can be le