When you think with full and strong concentration about something that you want to happen, and your mind does not resist the subject of your thought, your thought materializes.
The secret is concentrating, visualizing, seeing details, having faith and projecting mental and emotional energy into the mental scene. These are the general prerequisites. When your mind is empty from thoughts, and only one single thought is allowed to enter, it gains a very great power. One should be very careful with what he thinks. A concentrated thought is powerful, and exerts a very strong influence.