The first objective is to choose a carpentry hammer that you are comfortable with. These days there are many different types, shapes, and sizes to use. There are finish carpentry hammers, framing hammers, sheetrock hammers and more. Hammers come in different sizes so before a decision is made on use a hammer make sure that it feels comfortable enough to swing it. I recommend for beginners to use a 16oz hammer. It is very comfortable and also very effective.
The secret to swinging a hammer is to use your wrist. When hammering nails into an object remember that it is all in the wrist and nothing else. People who are new to swinging carpentry hammers sometimes use their forearms muscles to bang the nail in the object. This method is effective but also very tiring. Practicing with the wrist will bring more successful blows to the nail head. If I get to use my hammer all day long its like me being in heaven their something about banging in nail that gets my adrenaline going and keeps me feeling alive.
But the hammerhead is not the only part of the hammer there is also the claw. There are many hammers that have different claws on them so make sure that you pick the claw that you are most comfortable with. I enjoy using the old fashion claw nothing fancy. Here is a valuable tip when using the claw if you find your self-having a hard time getting a nail out of something. Put the nail between the claws and bend the nail from side to side as you are bending pull on the nail and the nail will come up.