ideal filesystem layout

I've been asked to assist a DBA with setting up a postgres system.
I cannot seem to find any documentation on how to set up the filesystem
in an ideal fashion, other than the usual installation in /usr/local/pgsql.

This is likely a FAQ, so point me to it if it is, but otherwise, how would you
set up a box for a largish database (around 2Gb)?  I have 4x18Gb drives to
play with, most likely as a single Raid5 50Gb volume.

Would you have a partition just for transaction logs?  How would you slice
up the box as a dedicated pgsql server?  The o/s is redhat.

Thanks!