Always depart from the runway closest to the terminal - climb until you intersect the descent profile - shut engines down during descent - delay gear & flaps until well past the OM - call for a tug to the terminal. All these are proven to save fuel.
Practically speaking - Buy an efficient aeroplane!
Treat your engines with kid gloves, keep the airplane clean and light, make COMAT a chargable item to your company's own departments, don't fly dense routes where traffic conflicts eat up your reserves -- It's not rocket science!
