NTW online only works with DMZ?

I forwarded all the ports that I am supposed to (i think). I couldn't connect to any host. I tried putting my computer in DMZ, and it worked. I heard this is unsafe, though. I am guessing this means I am not forwarding my ports properly... I have been recommended to look at portforward.com, but it doesn't have my router model (SMC D3GN). Do any of you know how to forward the ports on this model?

Checking the SMC website, there's a manual for that model modem/router; http://www.smc.com/files/AB/SMCD3GN_...UserManual.pdf

Configuration of port forwarding is on pages 43-47.