Get Your Heart in Shape
Strength training should be incorporated into your schedule two to three days a week. There are essentially two ways to do it: by lifting weights with moves like the overhead press and the biceps curl, or by using resistance machines. Most people don't have resistance machines in their homes, so it usually requires going to a health club or fitness center. You need to decide which you prefer: the privacy of your own home or the companionship you'll often find at fitness centers. Some women like a combination.
Even if you don't join a fitness center or gym, you may want to pay for a few day passes to get a trainer to help you learn some strength training moves—how to isolate the proper muscles as you lift a weight or push on a machine, how to lift safely, and so on.
It's important to lift or push against the right amount of weight. Too little and you're not challenging your muscles enough. Too much, and you're setting yourself up for injury. The right amount of weight to push or lift is an amount that you can move 10 to 12 times in good form before you have to stop. If you can do the move more times than that, the weight is too light. If you can't do it that many times, the weight is too heavy.
Never strength-train a particular set of muscles two days in a row. Muscles need a day off between strength-training sessions to heal the little micro-tears that enable them to grow stronger. (It is okay to do the same aerobic exercise two days in a row.)