In system config on the target you need to enable kernel debug specifying firewire of serial.
Hook the target to the host with tht relevant cable.
Turn off the target.
Run windbg on the host and set it to kernel debug on the relevant interface (firewire or serial).
Restart the target and it should connect and you will see a lot of debug data.
You then set the path in windbg for the symbols and code for your driver (and use the global microsoft symbol server for their code, search in help for symsrv), then you can set breakpoints and step through your code.