The plank will help you tighten up your abs in a short amount of time.

The simple push-up is great for improving your core strength.

The pull-up targets your lats and rhomboid muscles of the back, along with the biceps and deltoid.

The deeper your squat is, the better. Once you get down comfortably, you can start incorporating light weights into your squat routine.

Make sure you do a number of exercises to work different parts of your body - it's the key to resistance training and to getting results.