Good players are constantly playing not only good shots but good shots with the possibility of something else. Of course, if the ball is very tight they just play a good shot without deception because no deception is really possible. If it is very loose they just play a good shot without deception because no deception is really necessary. But where the ball is neither very tight or very loose there are always possibilities.
Every time you play a certain shot from a certain position you can create doubt which can be exploited the next time you are in that same position. As an example, if you play a good drop shot when you are in the front right court, then the next time you are in that position the opponent's mental computer is telling him to watch out for that shot again. It hurt him last time and he doesn't want the same to happen again. Your computer should therefore be saying "OK, I'll show him the drop but actually play something else" (probably deep straight or cross-court, or lob). (The computer may of course conclude that the same drop is appropriate again). If you never play the drop,then however good your drives/lobs etc, you are not going to create the doubt that will cause your opponent to lean slightly the wrong way thus forcing him off balance (and therefore making his next shot a little less effective). Running in an anticipated straight line is easy. The really hard work is in having to change direction.
Another example of deception is to shape to play straight but actually hit cross-court, particularly on the forehand. It is true that no player is simply going to rush early the wrong way to get the shown straight shot but it is not difficult to get an opponent to slightly lean the wrong way and be off balance. As well as making his next shot less efective it also of course has enormous negative energy consequences for him.
Another example is the dummy boast/ but drive (straight). The further behind you the ball goes, the more it looks as though you are going to play a boast. Therefore, if you get in a good square position to the ball, let it get past you a bit and then, with a good early backswing and delayed wrist action pull it back straight, the opponent will be sent leaning for the boast and the straight drive will do more damage than just an "ordinary" straight drive played with no deception. You have "added value". A typical scenario might be (each time from a similar position): drive, drive, drive, boast, dummy boast/ but drive, drive, drive ..... You should have done damage with the drives and then also with the boast and then, shaping to boast to confirm the opponent's worry about it, the dummy boast/ but drive will wrong-foot him also.
You are now beginning to "play the game". But remember that the above scenario - and all the many possible delay/ deception scenarios - takes time to develop. To get to the dummy boast/ but drive above (the 5th shot in the sequence) may take 10 minutes of play before you have had 5 shots in a similar position on court.
Both players' mental computers tell them what happened the last time the ball was in that position (particularly if it was a good pressure shot) so you can use that knowledge to show him you are going to do the same again thus confirming his leaning movement - though actually doing the opposite, forcing that fatigueing change of direction. Such scenarios are available all over the court, almost all the time.