how best to partition HD?

[mike newman]

not sure if this is the best place to ask this, but there seems to be
little documentation on the subject, so here goes.

i've been wondering about the best way to partition my disk for linux.
having recently popped an IBM GNX 40gig into my wallstreet, i am no longer
constrained by space. so i thought it would be a good idea to have one
partition for /, for the stock ydl distro that i will presumable upgrade
at some point and somewhat regularly, one partition for /usr/local for the
other software that i install and will upgrade independently of the OS
itself, and one partition for /usr/home, which i most definitely want to
conserve across upgrades and backup quite often.

but i notice that people often tangentially suggest a separate partition
for /usr or /var ... is that better than leaving them in the same
partition as / ? i honestly have no idea why i would separate these, but
would rather learn now while wiping my hard drive is a low-key affair.

with 40gig to play with, overkill is not necessarily a bad thing, but it
seems a little silly to make separate partitions for everything, and i'd
rather avoid the scenario of having  N gig free but spread into n little
chunks.

mike newman