3:33 in this video
The most classic chest/arm-building exercise is the basic bodyweight Push-Up.
To execute a proper Push-Up that not only builds your chest and arms but also saves your shoulders, you have to set up in the proper position.
This is a position with arms shoulder-width apart and feet evenly spaced.
I like to think of a Push-Up as a moving Plank, so make sure there is always tension in the core to keep your body straight.
Lower your body to the floor while maintaining a 45-degree angle with your arms relative to your body.
Again, this arm position will protect your shoulders and allow you to fully utilize your chest and arms throughout the movement.
Once you reach the bottom position with your chest touching the floor, forcefully push yourself back to the top.