I'm going to O"Hare today to fly home!
O' Hare is a great place to visit, but it's poor for spotting form the terminal. It's just huge. The radiating shape of the terminals obscures most of the views. Also, depending on the winds, the aricraft may be landing nearly a mile from the terminal. I've spent many an hour at O'Hare, and the best place to view aircraft is from the Delta gates (the end of concourse L) or the gates at the end of concourse K. These provide good views to the southern runways, and give nice views (especially the L gates) of aircraft taxiing between the northern runways and the terminal. On American, you'll probably fly into K or H, which are connected into a "Y" shape.