Diet high in calcium and weight baring exercise e.g. brisk walking, are both essential. HRT will help maintain bone density. If there is a family history of osteoporosis or you experience a premature meno or have other health reasons that make you more prone to reduce bone density, then ask for a scan. Supplements can be beneficial but Vitamin D is essential to help absorb the calcium. If you don't get at least 15 mins of sunshine per day, every day (preferable on arms or legs without sunscreen), then vitamin D deficiency often occurs. It is strongly advised you take a good dose of Vitamin D in winter.
The brisk walking or other weight baring exercise are top of the list - great for keeping blood pressure down and lifting mood as well. DG x