The main principle of hypnosis is to put the subjects into a suggestible state of mind and an implant the desired suggestions. In some cases, you do not want your subjects to be aware that they are being hypnotized.
For hypnosis to work best, you want your subject, to be relaxed and free of tension. Ideally you want them in a relaxed state of mind and a comfortable atmosphere.
When you are hypnotizing someone voluntarily, you can simply ask them to a cooperate. Have them try to become aware of the areas where they are tense and focus on them. Get them to concentrate on relaxing.
If you are going to hypnotize someone secretly, you can still try to get them relaxed and reduce any attention. Make sure there are no distractions like bright lights were loud noises.
The real secret to hypnosis is to get the subject to focus inwardly and enter that state of suggestibility or trance. once the subject is in the proper state of suggestibility or trance, you can begin implanting suggestions.
There are many courses and books that will show you the secrets to hypnosis. You can also find these secrets at websites such as hypnosis-x.info, or by searching the Web.