Shop for cheap airfare online. Visit sites such as Bing, Fare Compare or Kayak to compare prices for flights from Midway or O'Hare airports in Chicago to San Francisco International Airport. Some flights might be cheaper if you are willing to connect at airline hubs such as Denver or Dallas, even if the same airlines offer direct flights.
Call airlines and compare rates. If you prefer to talk to a live operator, call multiple airlines and discuss what discounts might be available for flights from Chicago to San Francisco. If you are in the military, or if you are flying because of a death in the family, the airlines might be able to give you better rates over the phone than those found on their websites.
Fly out of Midway Airport. Midway isn't always the cheapest airport, but it offers gate space to more discount airlines than O'Hare International. Discount airlines such as AirTran, Frontier and Southwest offer more fare specials and cheaper fares than major airlines like United or American. Midway also is geared more toward domestic travel than O'Hare, making it more ideal for airlines to focus their cheaper domestic fares toward travel to and from Midway.
