For a start you could try plugging it in, scanning, and seeing if anything comes through the serial port.
Just open a terminal window and run
$ tail -f /dev/ttyS0
If no action try 'dmesg | grep serial' to see what other serial devices you might have, and try those instead.
You could also try watching the serial port with a terminal program like kermit or minicom. If you want to do anything useful you will probably have to write an interface or application to capture the data from the port.
See the Serial HOWTO
if you want more technical detail.