You can exempt many things like printers, phones, routers, switches.....etc by using the OUI - the MAC address space apportioned to a company - to do automatic exemptions. Check your exemptions often and run dsquery against their names or IP's just in case.
This helps clean up large networks.
Also, any kind of scanner that can ID devices and spit out a MAC address list would help you winnow out the exemptions. Superscan or Languard....etc
nslookup works for these machines and are machines allowed to self-register in DNS?
We dont have any trouble with that here. I believe RSD pick up ARP/RARP/and DHCP requests.
Best practices is to have an RSD installed on your DHCP server for best pick up.