Cable crossover is a good exercise that is targeting mainly your chest muscles, but it also has some slightly effect on your shoulder muscles and your body control. It is pushing your chest muscles to their maximum.
To make it work, you will need a special cable machine for this exercise. Once you got it, put the pulleys on it, about on your head level. Place the weight that it suits you the most on both of the sides on the machine, and hold the pulleys in each of your hand. Step forward with your one leg. Your torso should be pushed just a little bit forward from your waist, just like on picture 1. That will be your starting position.
Once you are ready to start, push the pulleys forward, to your stomach level. Here the important thing is to not let your biceps to do the work and not to move your elbows. So your hands should be straight all the time. Push on the pulleys as you breath out, until both of the pulleys touch in front of you. Once they touch, you will feel the stretch in your chest muscles. Make a short pause, about 1-2 seconds. That will be your ending position, just like on picture 2.
Get the pulleys back to its starting position as you breath in, making sure you are getting them back the same way you have pushed em, then repeat. This exercise should be done in series. Make about 10-12 reps per each of the series. Add more weight on the machine each week as long as you are performing this exercise often. Also you can wary the point of the pulleys where they meet, while you are pushing them. Do not overweight the machine if you aren’t, you don’t want to hurt any of your muscle.