I'm usually either too cold or too hot. My comfort range is very narrow. But I would rather deal with the cold and add layers than be hot. If it's too hot indoors I get nauseous, and outdoors I just get pissy. I used to live in AZ, and you could not pay me to live there again. Anyway, I feel generally cold pretty easily, but the worst of it is my extremities. (And I eat enough candy corn, I'm at the very top of the range of "healthy" BMI). My DH is always shocked at how cold my hands and feet get during the winter. The worst is in the mornings when driving to work. Even with down/thinsulate mittens on, my fingers are freezing, so cold it's painful. I have to start wearing fleece gloves when it gets below about 55. If it's too cold inside at work, my fingertips start turning purple and my hands get so stiff I can barely type.

The older I get, the more I exercise, and yet the colder my hands and feet get. I was at my chiropractor's office this spring and there was a poster outlining symptoms of people with problems of various systems. One was the thyroid and so many of the symptoms rang true with me. I talked to my best friend about it, who is a Doctor of Osteopathy, she said people with borderline thyroid problems often benefit from iodine supplements, helps boost their metabolism and regulate their systems. I was just looking into iodine supplements when I got pregnant, figured I'd hold off on them until post pregnancy.

One other tip, I've heard that taking cayenne pepper supplements can help improve circulation and therefore make your extremities warmer. I tried this briefly, but my stomach couldn't handle the pepper (and there are very few things my stomach can't handle in the way of food).

A couple of my favorite tips for warming up:
Drink a hot beverage (duh).
Run hands under warm/hot water.
Throw clothes in dryer for a few minutes, then take them out and put them on immediately.
Stand in front of fire place (but we don't have one at home, so I do it when I can).
Stand on top of heating register so that heat goes up flannel pj pants.
Use hair dryer to send warm air up back of shirt (aaaah, love this one before getting into bed).

Oh, and those chemical hand/toe warmers are a gift from god. (Widely available during ski season at REI and other sporting goods stores).