Regular exercise is one of the best things you can do to improve your health. It should be something you enjoy doing so you can make it part of your lifestyle. If you don't like doing it, you probably won't stick with it for very long. I recommend reading one of Dr. Kenneth H. Cooper's books for specific suggestions on exercise. He is a world expert on aerobic exercise and is very motivating. He has a web site at www.cooperinst.org. If you're into high tech fitness, you may want to try www.biofitness.com. To estimate how long you will live, take a look at www.nmfn.com/tnetwork/longevity_game_popup.html.
For exercise: First establish frequency, then duration, and finally intensity. Gradually increase your frequency up to 5-6 times per week. Start with 10 minutes a day and aim for 30-60 minutes per day. Your maximum heart rate is roughly 220 minus your age. You should strive to exercise to get your heart rate at 70 to 80% of your maximum. Increase duration and intensity by a maximum of 5% per week. Warm up with some mild exercise such as jogging in place, exercise, then cool down (walking slowly for 3-5 minutes). Finally do some stretching exercises while your body is warm to keep limber and avoid injuries.
Some of your exercise should include lifting weights. It has even been shown to benefit 80-year-olds. It will help tone your body, speed up your metabolism to help lose weight, and decrease the risk of injury. It helps your mood and sense of wellbeing. Consider getting instruction at a gym or from a personal trainer. In general you need to start of gradually, but aim to do each exercise 8-15 times. If you can't do it 8 times, it's too much weight. If you can do it more than 15 times, it's not enough weight. As you get stronger, you will need to increase the weight. Muscles need time to rest and grow stronger after a workout. You should not exercise the same muscles two days in a row. If you want to do weight lifting more than 3 times a week, consider alternating muscle groups. For example, you might do the upper body on MWF, and the lower body and abdomen on TuTHSat. Make sure you warm up first and stretch your muscles.
If you have any heart or lung conditions please consult a health care provider prior to exercising.