If you're right-handed, take your left leg and pick it up slightly as the pitch is released. (It will be the opposite if you're left-handed.) As the pitch comes toward you, stride forward roughly a foot (less if you're smaller or younger) so you're building momentum toward the pitcher.
By now, you should have figured out whether the pitch is good enough to hit. If it's definitely a ball, continue your stride but watch the ball go by. If you think it's a strike, turn your hips through the ball and swing the bat.
Your back foot should pivot, but not leave the ground. You know you've done this correctly if your foot is pointing downward. You should feel your weight shifting forward.
Keep your elbows toward your body so the bat goes in a tight circle. If you're reaching for an outside pitch, you'll lose a lot of power. But if there's two strikes, there's little choice, of course.
Your bottom hand should be pulling the bat over the plate while your top hand guides it. You'll want to hit the ball just before it goes over the plate. Any later and you'll likely foul it off.
