Another trick is to look for routes that are heavliy served by an airline's feeder airline, but has one flight a day on the regular airline. The regular flight will tend to be overcrowded with people who need to make the route, but refuse out of fear or comfort to take the propeller flight. Book the jet flight, and take a bump to the (sometimes simultaniously departing) turboprop (or regional jet)!
This has worked for me (going from UA to United Express) on a couple of IAD-ATL flights as well as IAD-JFK and IAD-RDU.
[This message has been edited by Matt Wald (edited 02-18-99).]