If you are not familiar with, or do not have access to the djbdns command-line client tools, please note that dnsq TYPE NAME SERVER is mostly equivalent to dig @SERVER NAME TYPE +norecurse.
Using a.root-servers.net (198.41.0.4) to start my lookups.
$ dnsq a google.com 198.41.0.4 1 google.com: 500 bytes, 1+0+13+14 records, response, noerror query: 1 google.com authority: net 172800 NS a.gtld-servers.net [...snip...] additional: a.gtld-servers.net 172800 A 192.5.6.30 additional: a.gtld-servers.net 172800 AAAA 2001:503:a83e::2:30 [...snip...]
Next we'll try a .net TLD server.
$ dnsq a google.com 192.5.6.30 1 google.com: 164 bytes, 1+0+4+4 records, response, noerror query: 1 google.com authority: google.com 172800 NS ns1.google.com authority: google.com 172800 NS ns2.google.com authority: google.com 172800 NS ns3.google.com authority: google.com 172800 NS ns4.google.com additional: ns1.google.com 172800 A 216.239.32.10 additional: ns2.google.com 172800 A 216.239.34.10 additional: ns3.google.com 172800 A 216.239.36.10 additional: ns4.google.com 172800 A 216.239.38.10
And now, let's ask one of google's nameservers.
$ dnsq a google.com 216.239.32.10 1 google.com: 212 bytes, 1+3+4+4 records, response, authoritative, noerror query: 1 google.com answer: google.com 300 A 72.14.207.99 answer: google.com 300 A 64.233.187.99 answer: google.com 300 A 64.233.167.99 authority: google.com 345600 NS ns1.google.com authority: google.com 345600 NS ns2.google.com authority: google.com 345600 NS ns3.google.com authority: google.com 345600 NS ns4.google.com additional: ns1.google.com 345600 A 216.239.32.10 additional: ns2.google.com 345600 A 216.239.34.10 additional: ns3.google.com 345600 A 216.239.36.10 additional: ns4.google.com 345600 A 216.239.38.10
Yay! 72.14.207.99, 64.233.187.99, and 64.233.167.99; we're done, after only 3 lookups.