When you talk about chest exercises, the image in most people's mind is of large sweaty guys in a gym doing bench press with a bar that weighs as much as a small car. While that's certainly one end of the spectrum, the reality is that chest exercises should be part of everyone's workout routine.
The bench press can be done in a variety of ways - on a flat, incline or decline bench, with a bar or dumbbells. To really benefit from the chest exercises, if you use dumbbells, you'll need to use less weight. To perform the bench press, lie on a bench, with your butt, back, shoulders, and head flat. You can do bench press either with your feet flat on the floor, or with your feet up and legs bent - whichever you choose, keep you back flat throughout the movement.
Reach up with your hands slightly wider than shoulder width, and grip the bar. Inhale, lower the bar to your pecs, then immediately begin to move the weight upward. Do not bounce the weight off your body - it can cause injuries. Exhale as you drive the weight upwards, pause slightly at the top of the movement and then repeat.
A good alternative choice is dumbbell flyes. The starting position is the same as for bench press, but for flyes your arms should be kept slightly bent, with your palms facing each other. Keeping a slight bend in the arms, move them slowly in an arc away from the body, lowering them until a comfortable stretch is felt in your pecs/shoulders. Raise them along the same arc back to the starting position - a good way to visualise the position of the arms is to imagine you have a small barrel on top of you. Pause briefly at the top and repeat the entire movement.
As with bench press, this can be done on a flat, incline or decline bench. Two choices, endless variations, one result - stronger pecs.