How can I shrink LVM partitions?

I have installed a RHEL 4 guest OS on a non-preallocated disk, using automatic partitioning during the install. Now when I run vmware-toolbox to shrink the disk, only /boot is listed, none of the LVM partitions:

/boot     /dev/sda1

/           /dev/VolGroup00/LogVol00

swap    /dev/VolGroup00/LogVol01

where the two LVM partitions are on /dev/sda2. How can I shrink / ?