Effective exercises for improving cardiovascular fitness include activities that elevate the heart rate and challenge the cardiovascular system, such as running, cycling, swimming, brisk walking, jumping rope, and aerobic dance classes. Choose activities that you enjoy and can sustain for at least 20-30 minutes at a moderate to vigorous intensity. Incorporate interval training, where you alternate between periods of high-intensity effort and active recovery, to maximize calorie burn, improve endurance, and enhance cardiovascular health.