START SLOW if you haven't done much before. There's always a risk of injury or overexertion if you haven't been very active; so be sure to get clearance from your doctor before you start. Also, once you start your fitness activity, keep the time period short and the intensity low until your body adjusts to the change and then, methodically, increase the time and intensity until you get to where you want to be.
SET A GOAL. Losing weight, becoming fit and trim, getting all that extra energy, and avoiding future health problems are all benefits - not goals. Your goal should be to find a way to get vigorous physical activity into your weekly routine. This kind of goal is more practical and achievable. Once you get there the benefits will follow.
FIND AN ACTIVITY that is tolerable, if not fun; one that fits your lifestyle and is easy to do. This is important because fitness has a short shelf life. It fades fast if you don't keep it up, so you need to find something that you can do all the time, for a lifetime.
BUILD A SUPPORT GROUP. Try pulling your friends and family into your workout routine. You may be surprised at how those who first scoff at the idea quickly change their minds when they see you doing it.
KEEP YOUR EYES ON THE PRIZE. Don't get discouraged if you start a workout routine and you have a few slip-ups or miss a couple of sessions. Remember, you're trying to build a whole new habit and that takes practice and occasional failures. Just keep trying until you find what works. The more you practice, the easier it gets --- the easier it gets, the less you have to practice!