I beleive the guys working for the low cost would be an expert at it, otherwise In the Airbus FCOM , there is a “green procedure” Chapter which give you all the tips and tricks how to be fuel efficient. In a nutshell: Single engine taxi In & Out with minimum braking, Climb at CI zero (EasyJet Procedure), Optimum cruise alt, Idle power as long as possible during descent, Delay the configuration as much as possible and lowest flaps setting for the approach.