|Here are ideas.|
One is ubuntu connects to router either wired or wireless,
One is ubuntu connects to XP box either wired or wireless.
Router is easy for many people. Your system may not have a router or other reasons.
To connect to xp box you need two nics for ICS but can run single NIC with analogx's proxy. It doesn't limit you to a useless IP address.
"Best Practices", Event viewer, host file, perfmon, antivirus, anti-spyware, Live CD's, backups, are in my top 10