Getting there and away
Use Hipmunk.com and Kayak.com to search for flights, as they let you search with all kinds of criteria. Hipmunk even lets you sort by AGONY of a flight. Once you've found a flight, go to the airline website to see if you can get that flight for a cheaper price. Be sure to price it almost to the point of booking it, as many surcharges will not show up until just before payment is due.
Consider using the following destinations in your search:
CGN (Cologne/Bonn) DUS (Duesseldorf) DTM (Dortmund) FRA (Frankfurt) AMS (Amsterdam) RTM (Rotterdam)
- http://auskunft.kvb-koeln.de/cgi-bin/ASSRoute.cgi Public transportation in Cologne
- http://www.vrsinfo.de/englisch/the-vrs/vrs-about-us.html Public transportation in and around Cologne
- http://www.bahn.de/i/view/USA/en/index.shtml Public transportation all Germany