Because of the nature of CFS, it's important that you work with your doctor or physical therapist (PT) to build an exercise program that will both conserve and boost your energy. Exercising too much too soon could actually do more harm than good, especially for people with chronic fatigue. Your exercise needs to be calibrated properly so that you strengthen your stamina and avoid a relapse. Gradually increasing your energy expenditure can improve your CFS symptoms. One approach is to alternate between cardiovascular and resistance training -- and include gentle stretching before and after every workout.
A good training goal could be to walk 10,000 steps a day, which is considered an "active" lifestyle, and should take about 30 to 45 minutes to accomplish. Once you have your doctor's okay, you can start slowly: Walk 10-15 minutes daily, and build up. You might want to get a device called a pedometer that measures the number of steps you take, to keep track. Read the safety considerations, and watch the videos below, which outline some cardiovascular, stretching, and strength-training exercises you can include in your regimen.