DNS Internal and Extrenal

I have DNS installed as per Q172953 doc. for my registered internic domain name only. I have this set up for Exchange only. What is the proper procedure for DNS installation on my internal domain, which is not regitered.
I am running a PDC, BDC, Proxy (for web access, mail only), Exchange and a couple of stand-alones. I have DHCP and WINS running. What entries do I need to make to provide DNS internally without creating any recursive problems.

Don