If you've ever tried working out your chest, I bet you've done push-ups. Or, if you're an athlete, I bet you've done pushups during conditioning and practice. They are definitely one of the most widely used exercises, but they are totally underestimated. If you take your time to learn how to do push-ups correctly, it will make all the difference in your chest muscles. I'll go over some of the most important components of the "perfect pushup".
The first thing to remember while doing pushups, is that form is EVERYTHING. If you have good form throughout the entire push-up, it will isolate your chest muscles much better and you'll get superb results. When you are doing a pushup, you need to have your arms shoulder-width apart, a straight back, tightended buttocks, and straight legs, with your toes holding up your legs. As you are moving up and down during the motion of the pushup, you must keep your back straight, DO NOT, let it dip and arch, which is the natural tendency because it makes the pushup easier. I see people "cheating" like this all the time when doing pushups, and they really are only cheating themselves outta stronger, better-looking chest muscles.
Even though it makes it harder, keep everything straight as I mentioned as you SLOWLY drop down and push yourself back up with your chest muscles and tricep muscles. If you're doing it right, you'll feel a strong burning sensation in both muscle groups. Don't worry about that feeling and push through it, it is good for you; it's what you want to feel! Squeeze every once of burning sensation as you can, pinch your pectoral muscles (chest muscles) together at the climax of your push up. This reall works the pec muscles hard and that is what you're aiming for, because the more you tear them down, the bigger they'll build back up!
Keep going until you cannot lift yourself off the floor anymore. After that, rest for a little bit, maybe like 10 seconds, and then get yourself to the upper position. Now, ever so slowly, let yourself drop down to the floor again. Fight the drop the whole way down, keep your muscles as taut as possible.
Your chest muscles are exhausted, so you will inevitably fall, but if you fight against it the whole way you will experience intense burning and stretching in your pecs. Don't worrry, that is what you want! Once you're flat on the floor again, simply lay there and rest. Now, only 2 more sets and you're done! If you do 3 sets a couple times a week, you'll notice vast gains within 2-3 weeks, I guarantee it!