Captain Ron:
Some have reported that CWM - especially if the wipe is run through Rom Manager - doesn't quite wipe everything... leaving ICS remnants that might conflict with JB installation.
I would recommend that you Google a zip called "Android Revolution HD Super Wipe". While there are several Super Wipes out there, I can only vouch for this one. In one flash, it FORMATS /data, /cache, /Dalvik, and /system. It completely wipes every bit away.
Here'e my procedure for flashing Jelly Belly:
Make a nandroid of ICS, and then copy EVERYTHING YOU OWN to the PC as a backup... including your backups!
Boot into ClockworkMod from power-down.
Flash Super Wipe
Flash Jelly Belly 1.9
Flash gapps (I prefer the 7-1-2012 version)
Reboot.
Set up Android and stabilize the system.
If you want add-ons ( and you do
):
Power down the phone.
Boot into ClockworkMod from power-down.
Wipe cache and Dalvik
Flash 1% Circle Battery Mod
Flash Power Menu Reboot Mod
WIPE DALVIK CACHE AGAIN AFTER FLASHING!
Reboot.
Enjoy.
If you want any OTHER Mods, flash them in another CWM session. You don't want to flash them all at once.