One thing worth mentioning about coming to Chicago for football. The Bears' have one of the highest priced tickets in the NFL. Face value for upper deck between the 20-yd lines was $75 this year. Scalping-wise, I was able to sell my four tickets to the Bears - Bucs game (40 yd. line, upper deck, row 19) for $195 each to help finance the AZ trip!
Your best bet is ticketmaster the minute tickets go on sale - especially if they make it to the NFC Championship game or better. Most fans will go for gold - Bears vs. Packers. With luck, you can get seats in the upper deck for face value.