If you're just starting out and just want to build up your chest, then I'd recommend you do about 8 sets of chest press for 5 to 8 reps each. Use the most weight you can without having to break form. Proper form helps you prevent injuries and get the most out of your workout. Here are a few pointers:
** Contract your scapula, and maintain that contraction throughout.
** Keep your lower back slightly off the bench.
** Keep your elbows at an angle to your shoulder, roughly in line with your diaphragm. Don't keep your elbows in line with your
shoulder! That will mess up your shoulders.
** Try to keep your wrist straight, it'll work on forearms and lower the strain on your wrist when you move on to heavier weights.
** If you keep an open grip, when you get sweaty the bar could slip and fall on you.