That phrase is motorsport parlance but it can be used for everyday driving. Basically, short-shifting means you go up through the gears quicker than normal, thus using less revs at each gear.
My Dad's saying is always that you start damaging your fuel efficiency at 2000RPM. Cruising at 1500 is ideal.
Ease away from stops, don't bolt.
You would not believe the number of people I've spoken to who employ all these "measures" such as avoiding peak hour, using backstreets, even additives to the fuel tank, and yet they rev the crap out of the engine as they change gears and plant their foot on the accelerator as they go away from the lights. And it's kinda like, well, you just blew all your good work.