One of the keys to staying warm is to stay dry.

That being said, the layer closest to your skin needs to be something that "wicks" away sweat. Anything like polypropolene, silk, or I am have started wearing UnderArmor brand shirt - it's awesome. Make sure cotton is not the closest to your skin whatever you choose.

From that point - I normally layer depending on the tempature and what style hunting I will be doing. It really depends on the individual - wool is great at keeping you warm even if it's weat. Cabela's have down insulated pants that I use.

One thing I will do if I will be sitting for a long period of time is to carry as many of my clothes in as possible. That way I am not building up a sweat as I walk. After I get to my stand - I will add layers as chill sets in.