Do your research, put your plan together, and then implement the Firewall policies that best suit your unique environment.
References:
Anderson, Michael R., “Internet Security – Firewalls & Encryption”, New Technologies, Inc., January 17, 1998, Article 1, www.forensics-intl.com
http://www.thewall.com/wallx/wallxbrief.html
http://www.gelb.com/_vti_bin/shtml.exe/search.htm
http://www.isc.tamu.edu/tamu/firewall.html