I fly a C172. Here are some of our winter SOPs:
-Run the engine at 1000 rpm for 10 minutes before starting the runup.
-Idle at 650 rpm.
-Power reductions should not exceed 100 rpm/minute, and never below 1500 until the flare.
- no flights when field temperature is below -25C (-25C I've seen several places as a cutoff temperature for starting the engine without preheat, and we don't have preheat)
There was is a good bush pilot book that treats cold weather flying. It used to be free on the net here: <A HREF="http://www.fepco.com/BF.secI.ptIV.intro.html" TARGET="_blank">http://www.fepco.com/BF.secI.ptIV.intro.html</A>
but I see the author has taken down some of the chapters, and just tells you how to buy the book.