From: ecomodder
Here’s just one of their hard-core and one of their just plain-practical tips:
84) Avoid heater use until the engine has reached operating temperature
Engines runs rich until a minimum temperature threshold is reached. Running the heater blower before that has happened will slightly increase warm-up time and increase fuel consumption.
85) Avoid ‘warm up’ idling
Don’t idle your engine to warm it on a cold day. An idling engine gets zero miles per gallon.
Start to drive – under light loads – as soon as the engine is running smoothly (usually immediately). It’s a more efficient way to warm the engine and entire drivetrain, including tires.