Dressing for outdoor walks requires two things: The right coat and the right accessories.
For casual walking for more than 10 minutes, you need a coat that is very light but doesn't sacrifice warmth. Thermal insulated coats and puffer jackets are usually the lightest materials. Check out the Mighty Lite Hooded Jacket by Columbia. It zips up from just above the knee to the chin and has a hood. A hood lets you put a stocking cap underneath, if you need it.
If you walk a dog or walk to a store in the winter, you should also plan ahead for the right accessories. Leg warmers fit easily under most pants and over socks to provide extra warmth up to the knee. Some versions are even longer and include stirrups to keep them in place over your socks. Urban Outfitters, for one, also carries leg warmers that fit over the shoe or boot.
Arm or wrist warmers are a great choice for sitting at home reading or when going out. For going out, fit your mittens or gloves right over (or under) the arm warmers and you have another layer of protection. Check out your local home repair store for some that are specifically designed to protect thin skin from things like cat claws — this can be handy as well as warm.
On the other hand, puffer coats and insulated thermal coats are not exactly elegant. For a trip to church or dinner, you might want to wear a more formal coat. Add layers for more warmth and a muffler to help protect the neck. Also consider soft undergarments like those from Cuddl Duds. Pants and undershirts have a warm inside close to the skin and a slippery-textured outside to make layers easier.
Choose the right non-slip shoes, and consider a walking stick or cane for extra balance.