Many players telegraph the direction of their attacking shot. Often, the opponent isn't sure how he knows where you are going, he just senses it. That's because when he sees the same stroke pattern resulting in the ball going one way, and another stroke pattern going the other way, it becomes habit to react to it – even if he isn't sure specifically what in your stroke is different. (When you recognize a person's face, do you consciously see the distinct features that make this person's face unique?) So try to keep your shots identical as long as possible before committing to a direction, and even use misdirection.
For example, if you set up for a forehand shot as if you were going to the right (for a right-hander), your body might face to the right. At the last second, whip the shoulders around, and go to the left. Or set up like you are hitting to the left, but at the last second, rotate the shoulders back and go to the right. Or try hitting the ball "inside-out," where you set up as if you were hitting a forehand to the left, and at last minute hit the inside of the ball (relative to you) and go to the right. Do the same type of thing on the backhand, where you might set up to go one way, and then, at the last second, rotate your shoulders so you can go the other way. If blocking, you can make these last-second changes by just rotating the racket left or right.