It is easy to hypnotize a person who wants to be hypnotized because all hypnosis is, in the end, self-hypnosis. Contrary to popular misconceptions, hypnotism is not mind-control or mystical powers. You, as the hypnotist, are mostly a guide to help the person relax and fall into a trance-state, or waking sleep.
Covert hypnosis or conversational hypnosis is one of the most common method of taking control over others mind. However, you must remember that while you hypnotize someone you are not taking control over them, but you control their thoughts. You make them believe something that you tell them to be their own thought.