Having a technically sound movement pattern is a very important component of shooting (see my tip the Basic Jump Shot). Just as important, however, are certain mental abilities. These are concentration, confidence, and relaxation.
Shooting requires single-mindedness, that is, the ability to shut everything out of your mind, except the immediate task at hand. That task is putting the ball into the basket.
To help you develop this ability, you must develop a narrow external focus. Once you decide to shoot, you must concentrate on only a specific target. If you are shooting a lay-up, focus on a spot on the backboard so that, when the ball hits that spot, it will fall down into the basket. If you are shooting directly at the basket, focus on a pinpoint spot on the back rim which is directly opposite to you. In either situation, focus on that spot until after the ball has left your shooting hand and is well on its way. Once you decide to shoot, do not let anyone or anything disrupt that focus. To develop this ability practice focusing each time you shoot.
You must believe that each time you shoot you will score. Knowing that you are doing the 'right things' will help you sustain and nurture this attitude. Doing the 'right things' is knowing that the execution of every shot is consistent with its technically sound movement pattern and taking the good shot. An example of taking a good shot is shooting one similar to ones that you consistently make in practice.
Accurate shooting requires a high degree of flow, that is, your shooting motion should be smooth, continuous and quick. Consequently, when shooting, your muscles should be relaxed and all the joints should be loose.
It is very difficult to relax when you are unsure or hesitant. Being unsure or concerned about whether or not you will make the shot also makes it very difficult to concentrate.
This ability to relax is closely related to being able to concentrate on your shot and to having a feeling of confidence.