There are two factors that are crucial to the success of your physical activity plan. One is that you truly enjoy the activities that you do. There are enough choices that virtually everyone can find an activity he or she genuinely loves. For example, if you walk, find someone you enjoy walking with -- soon the walks will be the most fun parts of the day.
The second is that you have the support of your family. Talk to your spouse or partner about the need for physical activity and its importance for both of you. Each of you can set physical activity goals. When one of you reaches a goal, have the other cook a really tasty saturated-fat-free celebratory meal or give some other reward. It may sound corny, but encouraging someone to stay in shape is the best way to say, "I love you." It means you want that person to be around for a long time. Use physical activity as a way to be together in spite of busy schedules. You can tell each other about the day's events just as easily walking together or exercising on bikes at the gym as you can in front of the TV at home.