If you get too cold try standing up for a while. For some reason I stay warmer standing.

Alot of guys drop their draw weight by 5 pounds and shorten thier draw length a tad to account for the bulky clothing. Just make sure to resight your bow (obviously).

Also, most of your body heat escapes from your head. Use a ski mask style camo hat and a wool turtleneck to keep your neck warm.

The biggest problem I have is toes and fingers going numb. Those chemical hand warmers are pretty nice for that.

Finally, dress in layers. I like to put most of my warm clothes on at the stand to avoid sweating on the way in. If you sweat walking in, you'll be cold, wet, and miserable all day long.