The key is to find a girl who is a sports fan but doesn't really hold any allegiances. When I started dating the girl I'm currently with, she liked college football and watching the NHL and NFL, but wasn't a fan of any team persay, other than UMD football.
Well, a Caps game, Steelers training camp, and a Nats game later, she's now a Caps-Steelers-Nats fan. Best part is, she watches the Nats every night and will give me updates if I'm busy.