How do i forward my linksys router?

Alright i have a linksys WRT54G wireless router with nat type 3.When I test my internet connection it says on the bottom (Nat type 3 voice chat may be restricted). Also sometimes when I want to play Socom ftb1 online it doesn't find the online server. I have done mild research on google how to change to nat type 2. Now I want to know which ports should I forward so I can play socom online without problems. Please show an example and description in response tyvm.