This starts out as a simple question, but the networking gets messy (for me anyway

) rather quickly. I want to do screen sharing with a friend using Netmeeting. They are running Windows XP on an ADSL connection.
I am running Windows XP on a 2 router home network behind a Cable Modem. My initial questions are:
1. How do I find out IP Addresses to use? Netmeeting identifies both ends as having 192.168.xxx.xxx addresses.
2. Are there specific ports that will need to be opened on the firewalls?
3. Is there anything else I need to set up before this will work?
Thank you.