I can't speak for the Windows or Mac versions of NSLOOKUP (they all seem
to be different), but your basic GNU NSLOOKUP as implemented on most
unices and NSLOOKUP on VM seem to work pretty much the same.  You can
get help for them by typing NSLOOKUP at the prompt, then typing a
question mark at NSLOOKUP's ">" prompt.  Generally the commands you'll
use the most are
 
set type=xxxx         where xxxx can be A, MX, ANY, CNAME, etc.  ANY
                      returns whatever is cached for that host.
 
server inet-host      where inet-host is a FQDN, e.g., NS.SOMEHOST.EDU .
                      This overrides the default which is your local
                      name server.  You use this if you get a response
                      like "Authoritative answers can be found from:".
 
exit                  quits NSLOOKUP.  "quit" will be evaluated as a host
                      name.  :)
 
There's a lot more, but I rarely need anything else.
 
Nathan