Okay that last bit got my attention.
Hypnotism as I know it is the subtle art of manipulation by suggestion, the one and only rule being that you can't make someone do something that they absolutely do not want to do, and suffice to say once somebody understands how hypnotism works it's all but impossible to hypnotise them unless they're really willing.
There is a psychosomatic component, for example if you're sitting at a computer desk right now and I tell you there's a big nasty spider creeping over your foot on a subconscious level some part of you (the paranoid part) becomes really interested in what sensory information is coming from your foot. This acute focus can make the natural "background noise" of your nerve endings feel like an actual sensation, you don't know exactly what the sensation is but with the thought of a spider fresh in your mind your brain makes an intuitive leap and all of a sudden to you it feels like there's really a big nasty spider on your foot.
Of course this isn't limited to fear (although fear and anger do work particularly well, being very deeply rooted in the brain's architecture) you can also use hypnosis to a positive effect, we actually do it all the time, if you hit your shin on something you instinctively put your hands on it to alleviate the pain. If I remember correctly that works by correcting the mental map of your body, it feels like the shin is smashed but when you put your hands on it the process that recognises and associates the feeling of your hand touching your shin with your shin being touched by your hand (that you are touching yourself rather than being touched by something else) corrects the mental map, reassuring your brain that the shin is in fact intact.
The pain hasn't stopped, merely your perception of the pain has changed, you'll find there's many applications of hypnosis in pain management, google it, personally I've found the cold finger trick works great for relieving toothache (imagine your finger is freezing cold then touch your tooth with it as if to numb it with the cold).
Anyway getting back to that last bit in certain circles of hypnosis is used for more, well, recreational purposes, and then there's the psychic vampires who essentially do this when they "feed" on people's emotions, Mmmm goth girls. Well to answer your questions you've just got to be relaxed and open minded, ideally see the same hypnotist (or whatever) several times, the better you know them and they know you the easier it is, it's a trust thing and it helps if they know what angle suggestion your respond best to.
