There are several types of hypnosis techniques, including traditional hypnosis, Ericksonian hypnosis, neuro-linguistic programming (NLP), and self-hypnosis. Traditional hypnosis involves inducing a trance-like state to access the subconscious mind, while Ericksonian hypnosis uses indirect suggestions and language patterns. NLP combines hypnosis with language techniques to change behavior patterns, and self-hypnosis involves inducing a hypnotic state on oneself for self-improvement or relaxation.

Some experts in hypnosis can use the techniques of hypnosis to hypnotize someone instantly through conversation. This is called covert hypnosis. For more information on covert hypnosis and other forms of hypnosis visit hypnotizepro.com

There is no TM for Hypnosis in any of the versions of the game. Unfortunately, the only way to learn hypnosis is through breeding or your Pokemon leveling up. Level up haunter and it might get hypnosis.

You can get hypnosis training at local shops, or by a trained professional. Hypnosis training can be attained by going to many institutions in California, home of hypnosis training.

Technically, Gastly had Hypnosis at level 1 and by the time you catch it the move has been overwritten by moves Gastly learns at higher levels . So, you need to obtain a Heart Scale in the underground and take it to someone in Pastoria City, who will then be able to teach Haunter Hypnosis.