On a second serve your goal is to take control of the point, to attack the opponent. So it is very important to vary your position on the court to take advantage of second serves. Usually you are going to move into the court.
Maybe if your forehand is your weapon you are going to move left in order to get more
forehands. Make sure that you are using the best position possible on the court. Do not just return from the same spot that you return from for a first serve.