I spent 6 months commuting between France and Germany flying on a Sunday night in one direction and a Friday night in the other. To avoid waiting in airports for any length of time I hacked my boarding passes.
I was always flying in economy but I would check in on line and print my real boarding pass, then modify the PDF of the boarding pass and change it to a seat in business with whatever other indications where necessary for a genuine business class passenger (e.g. the word BUSINESS or PREMIUM in big letters). I got all that information by picking up a discarded boarding pass at the airport.
Then I could arrive at the airport and skip all the lines using my fake boarding pass to go down the special business class channel and then use my real boarding pass to board the plane.
I only did this at airports where boarding passes were manually verified.
Source: John Graham-Cumming