Push ups, do as many as you can. They are a good way to build up your arms and chest muscles. If they get easier raise your legs higher so that you lift more of your body weight.
Step2
Sit ups, helps strengthen your abdominal muscles.
Step3
Jumping jacks, good way to work out your heart.
Step4
Squats, good for building up your thigh and butt muscles. With or without weights.
Tips & Warnings
Breathing is very important. Try and think about your breathing and keep it consistent.