Everyone here is pretty much in agreement with the notion to increase airspeed in a head wind for best range -

For anyone wanting an in-depth description of "descent performance", There are two good sources on it:

USN TPS Fixed Wing Performance, Flight Test Manual (Chapter 8 'Descent Performance') - which you can download online

Aerodynamics for Naval Aviators


shdw,

I can understand how you feel about rules of thumb - this older, airline captain whose a great pilot (and seaplane pilot) had an interesting rule of thumb about fuel consumption - he said that if you divide the max HP of recip engines by 20, you can usually get a ballpark figure of fuel consumption in GPH at normal cruise. Seems to be pretty close from a 172 to a T-6G Texan. It left me scratching my head...