Whether you’re using five-pound weights or 15-pound weights, dumbbell curls are a great to tone-up your biceps. Stand with your feet shoulder-width apart, holding a dumbbell in each hand with your palms facing up. Fully extend your arms on each side leaving a slight bend at the elbow. Lift the weights slowly until the dumbbell reaches just below your shoulder and then slowly bring the weight back down. Make sure your shoulders are loose and your abdominal muscles are tight. Try for five to 10 reps and build up from there.