Sometimes it's hard to know how much weight is enough when you're trying to build a little muscle.

Rule of thumb: Don't start with anything higher than 5 pounds. Starting with lighter weights will help protect you from injury. Ultimately, you want a weight you can lift at least 8 times, but no more than 12. Adjust the weight as you get stronger.

Train to Threshold
Here's the RealAge approach to strength training. Do two sets of 8 to 12 repetitions, resting for about 45 seconds between sets. The muscles worked should feel pretty tired at the end of the set, as if they can't lift the weight one more time. This is called training to threshold, and it makes your RealAge younger! Check out this video for Good Housekeeping's take on some of the newest strength-building equipment.

Prime Your Posture
Form, too, is important when you strength train. Your head should be in line with your spine, and you should have a natural arch in your lower back. Don't lock your knees. Keep your wrists straight and firm. Pull your shoulder blades slightly toward each other and down. Lift your chest up and out. You should be able to steadily lift the weight while keeping your form. And remember to breathe! This helps keep your blood pressure in check. Set your workout goals with this personal tracker.

Check out this tip from the YOU Docs that makes workouts feel easier.

The RealAge Workout. Roizen, M. F., Hafen, T., Armour, L. A., New York: HarperCollins, 2006.