This is how the disk layout that I would plan for my setup (It's a Virtualbox) / - root : 500m. This will be 'a'. swap : 1G (so we'll always have enough space for a core dump), this will be partition 'b' /usr : 3g, partition d /tmp : 500m (we don't anticipate much use of this), partition e /usr/local : 5g, partition f /usr/X11R6 : 5g, partition g /home : 5g, partition h /var : 5g (that's a lot of system log files), partition j /var/www : rest of disk, partition k You can follow more specific instruction from here : http://www.openbsd.org.my/faq/faq4.html#Moredisklabel
Don't look your past, but look your future