1. Do not get into my car unless you are already warm. Stand by a fire, lean against a radiator, rub your hands together to create some friction—do whatever you have to do, but make sure your body heat is raging before you leave the house to get into my car.
2. Do not allow your body to lose its heat. Fleece and wool are particularly helpful in this aspect.
2a. There is one fleece blanket already in the car that will cover the driver (me) and the front-seat passenger. If you will be riding in the back, bring your own. The m&m costume in the trunk is available, but I can't vouch for its warmth.
2b. I'm serious about the wool. Wool socks (make sure your feet are already warm before putting them on) and wool mittens (same). I also recommend a wool sweater and a coat. And boots. The boots don't have to be wool.
3. Do not stop singing and preferably dancing. Songs you love and know the words to will distract you from the fact that you will be able to see your breath. Dancing creates more body heat, of course, and is also fun.
4a. Once we have arrived at our destination, do not feel like you have to wait for me to lock and unlock my door from the inside several times in order to get out before you do. If you want to wait inside the car you may, but you can also get out and start running toward shelter and warmth and I won't care.
5. Do not complain. I know that it's freezing and that my car jerks every time I stop and then have to go again and I know it's loud and I know it's hard to get into and out of the back. But chances are I'm doing you a favor by driving you somewhere, so let's just have fun.