You are returning serve and you are constantly getting aced. What can you do? You are standing in the deuce court; imagine there is a chair slightly behind the baseline on the center line. Also, there is a chair in the alley near the baseline. Now imagine your two best friends are sitting in these chairs. They are not paying attention to what is going on in the match. You are standing slightly behind the chairs on the baseline.
Right before the server makes contact with the ball move slightly in, like you are sneaking up on the ball. As the serve goes right or left towards the corners of the service box, think about protecting your friends from getting hit by the ball coming at them. By trying to protect your friends, you will actually cut off the corner. This will allow you to take the least number of steps to make contact with the ball.
Many receivers will move parallel to the baseline thus pulling them way out of position and fighting their natural body weight. The key to not getting aced is to be moving forward before the server strikes the ball and cutting off the corner, thus protecting your friends.
Remember, move forward, cut off the corner and protect your friend.
Good luck on the courts!