"If it's a short haul flight on a low cost airline, try to avoid the last departure of the day - that's the one that may be cancelled if delays have built up during the day."
Applies to any airline - and the last flight of the day often means you're parked at some unknown corner of an airfield rather than at a gate and have to wait for the only bus still working to ferry you all to the terminal- LHR is very good at this.