What's best to warm up before moderate exercise?

Stretch, start slow: Stretching of all muscle groups is likely the most important single activity, done prior to exercise, or as an exercise by itself, to prevent musculoskeletal problems, strains, injuries. A principle of the aging process, is start low, and go slow. Exercise, regular walks, keeping the mind and body active is the most important part of any lifestyle of living. But slow as you go.