Utilize Metra to see a lot of the Chicago area and mucho railroad activity.
Everybody's first choice would probably be a ride on the Metra BNSF line, get off somewhere along the triple track route (everybody has a favorite spot) and view almost constant commuter, Amtrak and freight action.
UP West line also has plenty of pleasant suburban spots to observe heavy freight action along with Metra trains.
A ride on the South Shore to Michigan City or South Bend offers plenty of unique views, including the street running in Michigan City.
A ride on Metra Electric to Homewood and its viewing platform allows CN freight, Amtrak and Metra action.
Heck, ride any Metra line and get a view of big time Chicago railroading.
Of course, there's always Roosevelt Road and its view of Union and LaSalle St. action action and Metra Electric/South Shore trains.
Ride the CTA, of course, to see the city upclose. Red Line north to Howard, then Yellow Line to Skokie or Purple Line to Evanston offers a nice slice of CTA operations _ subway, elevated, at level with grade crossings.
