port forwarding through two routers

For the life of me i have tried doing port forward through two routers, but have never succeeded in doing so. I can do it easily through one, but never two. I'm already very fimilliar on how to forward ports, i just need to know how to do it through two.

I need it to be done for both my xbox and my computer being in the same room, connected to a D-Link 524, which then connects to my modem/router D-Link DSL-G604T.

Thanks for ANY help on this.