Where can I buy playoff tickets

[greatwallofdallas]

I was wondering where is the best place to get playoff tickets at?
I'm from California, I've seen the Cowboys for pre season games in Oakland and regular season in San Diego. I usually have friends that I buy tickets from or local Craigslist adds. But I would like to go see the boys at ATT for the playoffs.
I've never been to ATT, any suggestions would be appreciated as far as tickets, parking, etc...