Well, lateral movement plays a key part on defense. Proper positioning also plays a key, too far and they can just shoot on you and and too close makes it easier for them to drive past you. One thing I do is (since I still haven't done the vert exercises) is too usually place my hand in front of him just to ruin his vision of the court (not sure if that's legal) and sag a bit, knowing that if the player isn't hitting his shots, he would either keep on passing it or would try to create by driving down the lane. Just be prepared to take the contact.