Port Forwarding or perhaps my internet connection...

I've been trying to play "multi-prey," but I get horrible time capsule lag on all servers. Do I need to configure my router to fix this, or is it an inherent problem with my internet connection (high speed point-to-point wireless)? I've played games online before (WoW and Warcraft 3 which both work just fine), but never a first person shooter. Any suggestions?