Linux partitions

I am installing Debian linux on my machine and wanted to know the optimal
disk usage for the various partitions.

I have about 33 gig of unpartionted space.

What size would be good for the following partitions?

/home - do I even need a home directory if this is a one user system?
/var
/tmp
/root
/boot - the boot partition I made 8 megabytes.
/swap - the swap partition I made 512 megabytes.
/usr

I installed this earlier and did not make the /usr partition big enough and
then could not install all the packages.