There are two basic things you need to know when you are setting up an exercise program . . .
1. You need twenty to forty minutes of aerobic exercise three to four times a week.
2. You need to include strength training at least twice a week, but preferably three times a week.
Most fitness experts highly recommend trying to exercise at the same time on those days; not a necessity but it helps get you into a routine and you're more likely to continue.
Be sure to start your routine with a warmup, and gradually increase the tempo. If you're following an exercise tape, it's fairly simple to know what intensity you should be doing. If you are running, try throwing in periods of faster running along the way, followed by slower running. This will really get you in shape.
Are you willing to do more? Do you need more info on how to stay fit without extra fatigue?
You can try out these Workout DVDs
