A320 : fuel efficient descent
The simplified minimum fuel flight goes as follows:
Single engine taxi-out
TOGA take off with minimum certified flap setting (maintain TOGA for 5min AEO)
Accel at 400ft (legal minimum) to best rate of climb speed (CI=0) with MCT.
Cruise at OPT level flying max range speed (CI=0)
Idle descent at green dot (NOT CI=0 as this defaults to 250/270)
Decelerated approach stable at xxxx ft
Landing with minimum certified landing flap
APU start 2 min after touchdown
Single Eng taxi-in
Ofcourse this is all very academic albeit simplified but good to keep in mind.