The push-up is the best exercise you can do to build muscles, lose weight, tone your arms, back and abs, and build endurance.  Push-ups also help to strengthen the entire upper-body,are good for stabilizing your joints, and are great to work on your abs as well.  Best of all you can do push-ups anywhere, with no equipment and even in a very small space.  Depending on you arm position, and leg position, and the amount of your weight you place on your arms, there are many variations of the push-up and over time it is best to mix it up, and try some of the other versions to give yourself a well-rounded workout:

1.  The Standard Push-ups
Purpose:
To strengthen the muscles of the entire upper body with special emphasis on the chest (pectoralis major/minor), front of the shoulders (anterior deltoid), and the triceps (triceps brachii).
Execution:
•    Lie down on your stomach with your hands on either side of the shoulders and your fingers spread.
•    With your feet together, get up on your toes by pushing your upper body away from the floor until your arms lock at the top (exhale).
•    Slowly lower yourself back down to the floor making sure to keep the entire body straight like a board (inhale), and then repeat without letting your upper-body touch the floor in between.

2. Modified Push-ups
Purpose:
An introductory push-up exercise to help strengthen the muscles of the chest (pectoralis major/minor).
Execution:
•    Lie down on your stomach with your hands on either side of the shoulders and your fingers spread.
•    Cross your feet and bend your knees then push your upper body away from the floor until your arms lock at the top (exhale).
•    Slowly lower yourself back down to the floor making sure to keep the entire body straight like a board (inhale), and then repeat without letting your upper-body touch the floor between repetitions.

3. Incline push-ups
Purpose:
To target the muscles of the upper chest (pectoralis major).
Execution:
•    Place your hands on a step or stair and lie face down on your stomach with your hands on either side of the shoulders and your fingers spread.
•    With your feet together, get up on your toes by pushing your upper body away from the step until your arms lock at the top (exhale).
•    Slowly lower yourself back down to the floor making sure to keep the entire body straight like a board (inhale), and then repeat without letting your upper-body touch the step in between.

4. Isometric push-ups
Purpose:
To improve the endurance of the chest muscle fibers (pectoralis major/minor) with some emphasis on strength and stability in the shoulder joint as well.
Execution:
•    Lie down on your stomach with your hands on either side of the shoulders with your fingers spread.
•    With your feet together, get up on your toes and lift your body about 3 inches off the ground.
•    Now HOLD THIS POSITION and do not move for as long as you can!
•    Remember to keep breathing consistently throughout and try to hold the position a little longer each time.

5.  Close-grip push-ups
Purpose:
To develop the muscles of the chest (pectoralis major/minor) and the triceps (triceps brachii).
Execution:
•    Lie down on your stomach and place your hands on either side of the shoulders with your fingers spread.
•    With your feet together, get up on your toes and push your upper body away from the floor until your arms lock at the top.
•    From there, move your hands directly into the centre so that just the thumbs and index fingers touch.
•    Slowly lower yourself down to the floor making sure to keep your elbows tucked into your side (inhale).
•    Just before you are about to touch the floor, push back away towards the ceiling(exhale) and then continue like that until your desired repetition range is achieved.

6. Push-ups on the Ball
Purpose:
To develop the muscles of the chest (pectoralis major/minor), shoulders (deltoid group), and triceps (triceps brachii).
Execution:
•    Start by kneeling down in front of the ball and then roll forward on top of it so that the ball is resting under your upper thighs, knees bent, and legs crossed with your arms at shoulder-width apart on the floor.
•    Slowly bend the elbows bringing your upper-body closer to the floor (inhale) until your nose almost touches the ground.
•    Push yourself back up to the top (exhale) and then repeat the process.

7. Reverse Ball push-ups:
Purpose:
To create stability and strength in the shoulders (deltoid group), chest (pectoralis major/minor), and arms (biceps and triceps brachii)!
Execution:
•    Start by lying face-down on the ball.
•    Place your hands at “10 & 2″ on either side of the ball pointing down.
•    Squeeze the ball as tight as you can for stability and push the ball away from you (exhale) until the elbows lock.
•    Slowly return to the starting position (inhale) and repeat without letting your chest touch the ball between reps!!

8.  Clapping push-ups:
Purpose:
A very intense exercise to help maximize speed agility and strength in the chest muscles (pectoralis major/minor), and shoulder joints)!
Execution:
•    Lie down on your stomach with your hands on either side of the shoulders and your fingers spread.
•    With your feet together, get up on your toes by pushing your upper body away from the floor in an explosive manner until your hands get off the floor and perform 1 clap with your hands in the air (exhale).
•    Make sure to get your hands back into the starting position as soon as you land in preparation for the next rep  (inhale).
•    Pause only briefly at the bottom and then continue repeating the explosive pushing motions until the desired number of repetitions is achieved.