Warm-Up: Do three minutes of cardio before your arm routine to increase your heart rate, loosen your muscles, and help avoid injury. Jumping rope, climbing stairs, and walking on a treadmill are great options. Once your torso begins generating a little heat, do two sets of 24 small (about five inches in diameter) arm circles to warm up your biceps, triceps, and shoulder muscles. Move your arms forward for the first set, backward for the second set.
Cooldown: Stretch the muscles you just worked to reduce soreness and maximize flexibility. Sit in a chair, extend your arms in front of you, one over the other, and clasp your hands to stretch out your biceps. Switch arms and repeat. Then bend forward and clasp your hands behind your back. Lift them gently for a deep stretch in the triceps.
Tip: If you don't have hand weights, use cans of food or water bottles filled with sand or uncooked rice.
From Real Simple: The Secret to a Better Workout
Push-Pull Kickback
How to Do It: Stand in a squat position, legs shoulder-width apart, knees bent at about 45 degrees, and chest leaning slightly forward. Hold a light dumbbell (three to five pounds is a good starting point for all these exercises) in each hand, palms facing your thighs. Bending your arms, bring your fists up toward your torso, in front of your armpits. Push the dumbbells straight out in front of you, fully extending your arms, knuckles up. Bending your arms, pull them toward your armpits and extend them back behind you until they're straight (shown). During this part of the exercise, pretend your upper arms are glued to your sides to better isolate the triceps. Do three sets of 12 repetitions.
What It Does: Works your chest and triceps. You'll see results along the backs of your arms and in the area where your shoulders meet your chest.
Shadowboxing
How to Do It: Stand upright, legs spaced slightly wider than your shoulders, hands in front of your face (like a boxer getting ready for a bout), with a light dumbbell in each hand. Extend your right fist as if you were hitting someone in the face, angling the punch toward the opponent's opposite ear. As you pull your arm back, imagine that you're ducking an incoming punch and bend your knees into a squat. Stand and repeat with the other arm. For the next punch, move your fist in a rapid upward motion, as if hitting someone just under the chin. Squat, stand, and repeat with the other arm. For the last punch, extend your arm as if punching someone on the side of the jaw with your knuckles (shown). Squat, stand, and repeat with the other arm. Do two to three sets of punches, 10 seconds for each set.
What It Does: Works your biceps, triceps, shoulders, and upper back -- the whole package. The squats will develop your glutes and quadriceps. The rapid and dynamic moves will give your heart a workout, too.
From Real Simple: Stretching 101
Double Biceps Curl
How to Do It: Stand upright, feet close together, knees relaxed. Hold a dumbbell in each hand, pressing your elbows close to your sides, palms facing forward. Bend your arms so your forearms form 90-degree angles in front of you. Squeezing your biceps, slowly lift the weights up toward your shoulders. Lower your arms to the starting position. Palms facing up, slowly curl your arms back up, this time to the outsides of your shoulders (shown). Again, remember to press your upper arms tightly against your sides to really work the biceps. Do three sets of 12 reps.
What It Does: Works the very centers of the biceps from multiple directions, creating chiseled definition.
Standing Push-Up
How to Do It: Stand facing a desk or a sturdy ledge. Place your hands shoulder-width apart on the surface in a push-up position and place your body at a 45-degree angle with the floor. Pull your navel inward and balance your weight on the balls of your feet (shown). With elbows close to your sides, bend your arms and bring your chest toward the desk as low as you can, inhaling as you descend. Slowly push yourself back up to the starting position, exhaling as you rise. Do two to three sets of 8 to 10 reps. To increase the challenge, do half the sets underhanded, gripping the desk or the ledge from below. This focuses the benefits on the lower triceps, which most women have a particularly hard time firming up. As you improve, intensify the exercise by moving your hands closer together.
What It Does: Strengthens your triceps as well as your abdominals and shoulders, which can improve overall posture.