||Call (800) 225-5303 once you are in the baggage claim area.|
Tell them you are going to the Orrington Hotel in Evanston from O'Hare and they will ask from which airline.
They will tell you a cab number and to wait outside from a certain exit (each exit has a number).
Cross the first road and wait at the second for the correctly numbered aqua & white colored 303 Taxi.
303 also services Midway Airport. The fare will be around $50.
Continental Airport Express|
A ticket must be purchased first. Ticket counters are in the baggage claim areas at Doors 1E, 2D, and 3E.|
Much more information is here.
Call (888) 284-3826 to make reservations to O'Hare.