Unfortunately once the LUN is created you can only check which igroups the LUN is mapped to and therefore which hosts can mount the LUN. You could add a comment to each LUN using the `lun comment` command, syntax as follows:
lun comment lun_path [ comment ]
Another way to keep track for future LUNs would be to include the hostname or clustername in the volume or qtree name, that way the output of `lun show` would show quite clearly which hosts would mount which LUNs.
With regard to training, there is some excellent documentation in the NetApp Tech Library which may well cover the information you require: http://www.netapp.com/us/library/