Staying warm on your stand seems to be a hot topic; and I understand why. Here's some things to consider when trying to keep warm.
1. Begin cold can make you miss. Being cold combined with the excitement of seeing a deer can make you shiver and ultimately miss your target.
2. The key to staying warm is to understand where the worst places are to get a cut -- head, groin, upper torso under the arms. That's where major arteries go and where more of your warm blood is at any given time. Keep these places warm and it will help keep the spots that normally cause trouble warmer as well.
3. Hats. Wear a warm hat that traps air and keeps your head from getting damp. If your head is damp with sweat from walking to your stand, go sans hat till you get there or change hats when you arrive.
4. Torso. The key here is staying dry and blocking the wind. I go with a down vest or jacket under a silent coat when it really gets cold. Nothing insulates like down if you keep it dry.
5. Neck. Wear a neck gaiter. Your corotid artery pumps a lot of blood through there and you want to keep it warm for the return trip. Put it on when you arrive at your stand. A fleece gaiter over a wool or polypro zip up shirt is a good choice.
6. Groin. Don't layer up too much here. Sit on a pad that blocks the wind and cold. Choose an Ensolite type pad or one that doesn't expand with lots of air pockets (think sofa cushion foam). It will both block the wind as well as keep the cold at bay. Wear wicking underwear to pull moisture away from the skin.
7. Overall. Take rain gear even when rain isn't called for. I keep mine in a waterproof stuff sack that I can compress to a small ball so it doesn't take up much room in my pack.
Avoid cotton. The rule is "cotton kills". Cotton absorbs moisture not only from your body, but also the air around you. Non-absorbent fleece is great in areas where you are prone to sweat, but combine it with a wind-proof layer.
8. Typical cold spots. Most people worry too much about hands and feet. If you pay more attention to keeping your head and core warm, your blood will stay warmer and as a consequence, keep your hands and feet warmer. That said, here's a few extra tips: If it's not too, too cold, use a muffler for your hands and leave off the heavy gloves which can cause your hands to sweat too much and just make them colder. The guy who says put socks over your hands and wrists -- good idea, use wicking socks to pull the moisture off your hands to keep them warmer. Wool is a next best choice. Better are those fleecy socks. When it is really cold, I might put a hand warmer in my coat pocket to rub on my face now and then if I'm not wearing a balaclava, but I avoid putting them in my gloves or pants pockets -- both of which cause me to sweat. For the feet, avoid foot warmers -- they'll just make your feet sweat and get colder. Be sure to wear insulated boots (800 grams or better) and wear a wicking sock liner under a pair of wool socks. Don't get boots that fit too tight, or consider loosening up the laces when you get on your stand to let the blood circulate better. Stand up now and then. Use a foot rest so your legs don't compress on your seat which can constrict the blood flow. You can also tie on an Ensolite pad to your stand base to restrict air flow under your soles. And if you're going to be out for a long time, take a pair of down booties and put them on in your stand.