There is one VERY important piece that is left out of most threads.
The newest Xooms that were release overwrite CWM files upon reboot unless you take specific steps to make sure it doesn't... e.g.
have the update.zip you want to use preloaded on the sdcard via pc
or
use a usb with a otg and a version of CWM that can apply update.zip from the USB drive.
Also beware of threads that dont mention what version of the OS they are for. For example its very easy to root your device, but it be on an on 3.x OS and then the OS will update it to 4.04 on the next boot cycle, and wont give you a chance to pick your ROM update. As a result your device is not rooted at this point, and CWM is not installed because you didnt have root in time to move these files:
adb shell mv /system/recovery-from-boot.p.old /system/recovery-from-boot.p
adb shell mv /system/etc/install-recovery.sh.old /system/etc/install-recovery.sh
while in root.
Really sucks.
So in a nutshell those with the latest Xoom tablets that were released, must make sure you find a update.zip that is compatible with ICS 4.04 and then get it to your SDCARD or USB Drive via any method possible - and then flash the right CWM that supports what you want to do, then catch that as it reboots the very first time but pushing the down button and then up button of the volume controls, and then you can install the root (update.zip).... then if all is well you will be able to boot normally, and then go back and get into CWM and install the ROM of your delight.
Experts feel free to chime in so I don't mislead anyone. I wouldn't follow the above advice until an expert puts their AOK on it.