You want to be cold when you start out. Add layers if you need them. If you start out too warm and don't remove layers soon enough they'll be all sweaty and then you have wet clothes. Your body temp will drop fast when you stop. Always have layers to add when you stop. That's when the warm parka comes in.
Seriously, I have hiked in winter in a tank top and been plenty warm. depends on the conditions of course. Managing your body heat is one of the most important things you need to do. Even polypro wicking clothing will take too long to dry when you're standing around cold. I usually bring at least another dry shirt to change into at the summit.
I learned this one the hard way: always bring dry socks, a small towel and some plastic bags. If your boots get wet you can dry your feet, change into the socks, then pull the plastic bags over them and put your feet back in the wet boots where they should stay dry for a good while. Hopefully long enough to get out of the woods. You can buy plastic vapor barriers at different outfitters or just use bread bags like your mom did when you were little.