Overhead lifts, like the classic overhead press and push press, are an important part of a well-rounded exercise program. Your shoulders and chest work cohesively to help you push heavy weight, so practicing your vertical press will help your bench press, and vice versa.
Push presses are fun because you get to use some leg drive to help get the weight over your head. Bend your knees about three inches, and push out of your heels. The energy you create with the leg bend will transfer into your shoulders as you move the bar. This will allow you to lift slightly more weight than with a strict overhead press.
Once the bar is over your head, make sure you push your head through your arms. The bar should be up and over your head, not in front of your chest. You want to end overhead lifts with the bar over your center of gravity.
Now get under the bar and make some gains!