Hey, the siddhis are acquired through long practice of advanced meditation. Ideally, the siddhis develop most fully after the awakening of the kundalini. At that point, your increased and controlled bioelectricity will allow you to have a strong command of the siddhis. But of course, each siddhi is different. For example, reading thoughts has more to do with mastering your own thoughts. You must be able to silence your mind in order to receive those of the person you are focusing on. This is where the importance of concentration, intention, and will comes in.
I suggest you read this: Power Meditation SIDDHIS