I do not think keeping the heat off until the engine got warmer would help. I would suggest a plug in engine warmer, they are cheap and easy to install. They cut the warm up time for your engine by half or better and also help preserve your engine in really cold climates. Parking in the sun if you can also helps.
A very late addendum:
Start driving! It will get your car warmer quicker then anything. Modern fuel injected gas vehicles do not need long warm up times to run properly and safely with the proper oil and anti-freeze. Anything longer then getting oil pressure is wasting fuel. Warming up your engine at an idle is simply a waste of fuel and causes a lot more wear on your engine then driving away.
In extreme cold like sub zero temps one should be using engine heaters to avoid frozen radiators and oil turning to a grease like gunk. If you have the engine heater you do not need to warm a modern fuel injected engine beyond a very short time in extreme cold. Also extreme cold is very dangerous to drive in and unless you really need to, don't.
Diesel engines are a little different. Diesel combusts poorly when the engine is cold. In a cold diesel the performance can be so bad that driving could be unsafe, and fuel is wasted.
Your heater will reach useful temperature faster if your engine heats up faster, as it takes its heat directly from the engine (usually by water heated by the engine block) - and the engine block heats up faster under load, so:
While the engine is warming up, select recirculate if your airflow has that option. This means you are just heating the air in the car, not having to heat cold air coming in.
Keep the air con fans on low until you start to feel warm air, then select incoming air.
Use a piece of cardboard or Coroplast to block airflow through the radiator. Do a search on "grille block" for details.
@darthness: The only real hazard I can think of is that you forget to take it out in the summer (or if you have to climb mountains), and the engine overheats. But that's why we have temperature gauges, and aftermarket OBDII scanners :-) I don't have pictures, and details are going to vary depending on your particular car.
@yankeekilo: To a certain extent that might be true, depending on whether or not you have a thermostatically-controlled fan or not. But I'm assuming educated drivers, who know enough not to waste gas by leaving their engine idling for long periods.
-30 this morning in Fairbanks Alaska. If you really want to know how to warm and maintain a vehicle during a truely cold winter (not the stuff a lower 48er considers cold) you need to ask an Alaskan or Canadian. Here is a list for you to do a search on:
... or if you want to save money just build a heated garage
First thing, park in the sun.
Beyond this, we're assuming a gasoline or diesel engine, not a hybrid or electric vehicle (most of those have electric heaters and will start blowing hot pretty quickly anyway).
If, like me, you leave home for work before the winter sun is up, or must park under cover but without heated space, your engine will warm faster with the heater off (it acts like a radiator, but without benefit of a thermostat to control coolant flow through its core), and under load. Don't turn on the air conditioning, but do turn on lights and (electric) rear defogger if available. Don't run the heater fan, and set the temperature control to cold (you want to close off coolant flow through the heater core).
Now, move off as soon as the oil pressure is normal (warning light out or gauge in range). Watch the engine temperature gauge, and turn on the heat or front defogger (as you choose or need) as soon as the temperature is off the peg, or at least two minutes after startup if you don't have a gauge.
These steps will give you the fastest engine warm up, hence soonest useful heat, and avoid wasting fuel at idle (when you're getting zero miles per gallon), as well as limiting engine wear (a cold engine doesn't wear faster under load than at idle, but warms faster under load). In that light, if you have to deice the windshield and windows before departure, scrape before starting the engine. The exercise can warm you, a little, and if you're properly dressed the weather won't chill you or your hands.
Once you're on your way, drive with appropriate caution; watch out for ice, especially on bridges and overpasses.
Revving the engine will make it warm up faster but it is not a good idea to rev a cold engine. The metal parts are contracted so extra gaps. The oil is not warmed up. You should let it just idle for at least a couple minutes. The oil will warm up pretty fast. You should see the oil pressure come down a little bit when the oil warms up. I wait for the idle speed to come down.
When it is cold the engine will just circulate water in the block. The block is massive so there is a lot of heat capacitance. The transmission will also pull off heat.
I wait to see the temperature gauge move and then turn on the heat / defroster.
Or you can just turn on the heater / defroster first thing. Yes it will take longer for the engine to warm up but you will also get some heat in your vehicle.
Don't rev the engine or accelerate hard until it is up to normal operating temperature.
Turn on lights and electrical heater(s) is good for a light load.
If you are in a hurry I suggest a heavy coat, hat, and gloves. If you let it idle a full 15 minutes to heat up that is a bit of fuel. If you are willing to drive easy the vehicle is ready to go after a couple minutes. If you only need to drive a few miles then just gut it out.
Window fogging up and deicing is another thing. Recirculate to hold in heat but you will need to to bring in external air if the windows fog.
My hack is wear more clothes.
Seems something is wrong with your car. 15 min is too long period i guess. Check if your thermostat got stuck in "long circuit" position, when the main radiator become a part of water circuit.. Because when the engine is cold, the thermostat must be in "short circuit" position and the main radiator is disconnected from the cooling circuit for more fast engine heating.
Ensure the radiator fluid is not worn out. Freshen it up, flush and replace anti-freeze to see if that fixes it.
My life hack for this is to run an extension lead out to the car with a fan heater and one of those mechanical timers (with the little plastic tags you press in to activate 15 minute intervals).
Half an hour of dedicated heat in a morning before the commute lasts long enough for the cabin heat to take over when the engine has warmed, and having the glass be warm will aid defrosting the outside, will demist/defog the inside and help prevent re-icing/re-fogging of the glass.
It's most helpful if you then don't run the blower as this will import cold air from the outside, unless you have the recirculate control on (which can prevent cold fresh air entering at higher car speeds and help maintain cabin warmth, though remember to switch recirc back to fresh to prevent accumulating moisture making misting/fogging worse tomorrow)
In terms of warming the engine, just drive it. Don't idle the engine - not only is it illegal in some jurisdictions it can put you at risk of having your car stolen, it costs more money than using a fan heater and it is not an environmentally friendly course of action. Having the fan heater timed means your car is warning while you're busy doing other things. Aim to purchase a fan heater that deactivates if it is tipped over or if the exit blower stream is blocked (overheating protection)
As noted, avoid running the blower; blasting cold air in your own face won't make it appreciably longer before the engine has warmed the coolant enough to provide some cabin heat, but it will certainly make it feel that way. Humans experience flowing air as cooler than still air for a couple of physical reasons (look up "windchill")
Keep your air con on; it will decide itself when it needs to deactivate (most systems turn off if the incoming air is too cold and the climate control wont succeed in reducing its latent humidity) and for the most part it keeps the air more dry inside the car. A car with a damp interior warms more slowly because heat energy is used in evaporating moisture from surfaces
Covering the cabin glass with a blanket can helpful to this "preheating with external heat source", as well as helping prevent icing of the glass
Other options to consider, though none of them are really lifehacky unless youre making them yourself as they all rely on a bought solution of a product intended for the purpose:
Frameshift: Don't wait for the car to warm up. Warm yourself directly:
A car seat warmer will pull energy directly from the electrical system to start heating within 60 seconds rather than waiting for the entire mass of the engine to heat up before you start feeling warm air.
This shouldn't have much impact on the battery or electrical system as the seat only uses 45 watts of energy compared to the car's engine which requires as much as 4800-12000 watts for ignition. (400-1000 Amps x 12v)