The only real way to work out the chest is through compound free weight exercises. People may argue that chest fly machine would be a good chest exercise. Don't get me wrong it is a good exercise but it is not the best compound chest exercise.

Top 5 Compound Chest Exercises

1. The push ups - Yes people, the simplest form exercise is the number one. Push ups uses your body weight as a resistant. You can virtually do this compound exercise anywhere all you need a surface. The push can be modified to a incline push up ie: hands on a bench, to make it easier. Or a decline, where your feet is on the bench, this will make the exercise much harder.
2. Flat Barbell Bench Press - Just like the push ups but with weighted plates. This is the next progression from a push up. Once push ups becomes to easy were you can 30 or more repetition you must do this exercise. In order for your chest to grow bigger and more defined the chest muscle must feel more resistant.
3. Dumbbell Flat Press - The main difference between this exercise and the flat  barbell bench press is that each hand will operate independently from each other. This will make your muscle more balanced. It will also require more core due to each hand having to balance the weight.
4. Incline Barbell Bench Press - The angle will make a big difference on how it work your chest muscle. The incline angle will focus more on your "upper" pectorals. This exercise will give you that "Big Chest Look"
5. Incline Dumbbell Press - The next progression to incline barbell press. It will require the same things that a dumbbell flat press would.

That is the top 5 compound exercises.