Sorry I can't give you advice about locations outside the terminal.
I've been there twice in the past year for photos and I just stayed
inside the terminals. I'll be there November 4-6 and I do plan on
renting a car and getting around, so I too would like to get my
hands on some good spotting locations outside the terminals.
The following is an old page from my website that is no longer up.
Some of this might be a little outdated...I'm sure somebody will
bring it to our attention if so:
**Begin cut and paste**
In the morning I like to go to the end of Concourse E, Terminal 2.
A lot of United Airline's aircraft taxi by as well as US Air, TWA,
and Air Canada. Depending on the winds you'll also see all types
of aircraft turning off the runway. Window glare is a major problem
at O' Hare, but here it's almost non-existant.
(NOTE: June 25, 2000): Continental Airlines is now using some
of these gates so this location now has more equipment parked
at the gate, restricting views
Another good morning spot are the north ends of
Concourses B and C (near gates B-17 and C-32 respectively).
United's 777's and 747's use gates B16 and B17 mostly and the
DC-10's and other 747's use C-16 through C-18. At this spot you'll
mostly get United Airlines aircraft.
In the afternoon I wander over to the end of Concourse F, Terminal 2.
This will get you mostly American Airline's aircraft taxiing by with
some runway action possible, depending on the winds.
My favorite location inside the terminal is at the end of Concourse L,
Terminal 3 near the Delta Airlines gates. This is about as close as
you can get to Terminal 5, the international terminal, without a boarding
pass. You get a good view of the taxiway and aircraft parked at
Terminal 5. Depending on the winds, there can be lots of wide-body
aircraft taxiing by. This spot is best late in the day when the sun is
behind you. Be mindful of the window glare though. There are places
here to shoot at to avoid it.
There are two bad things about O' Hare the makes photography tough.
First, there tends to be a lot of equipment constantly moving around.
It can be a challange trying to photograph an aircraft and not get the
baggage carts or the fleet services trucks in the frame. It's just a busy
place! Second, the gates do not have a lot of space in between them
and the jetways tend to extend from the terminal building at very sharp
angles. The result is is that there are many locations throughout most
of the terminals where you just simply can't see anything.
A noble spirit embiggens the smallest man...