Before undertaking any form of strenuous exercise it is important to warm up. Ten minutes of gentle warm up exercises will get your body mobilised and your muscles ready for exercise, making you less prone to injury.
Your exercise routine should include Aerobic (makes you out of breath) and Strengthening (hurts!) Exercises.
Aerobic: Shadow boxing; Clench your fists gently and begin by jogging up and down on the spot with your fists near your face. As you jog, extend one arm quickly straight out in front of you and return - as if punching someone in the face! Repeat with the other arm; continue for five minutes. Next stand with your feet quite wide apart, your hands still clenched up by your face. Transfer your weight from leg to leg, bend your legs as you transfer and swing your body weight from side to side - as if dodging punches. Continue for five minutes.
Strengthener: Burpees; Start in a squat position on the floor; feet together, knees bent, hands on the floor in front of you. Taking the weight on to your arms, jump your feet so that your legs are straight out behind you. Immediately jump them back in. Then as you transfer your weight to your feet, push upwards stretching and leaping into the air with your arms above your head. This is really tough, it will become easier as you develop a rhythm and get stronger; you should aim to do 20.