2 NICs in Windows Server 2K8. Confusion in IP settings please help…

My main computer has 2 NICs, one to be used for internet and other for local network computers. This IP configuration part is very much confussing (i m a novice in this part).

i want to share internet connection to lan computers from second NIC.

How do i configure ip addresses for both the NICs?

Current Connection:
Internet–>Router–>Main computer–>Switch–>LAN comps.

Please don’t say to change the connection mode… thanks in adv.