Induction can be instant, as Dan says that is good for party tricks and stage hypnosis, however for anything else I would be more inclined to use gradual induction methods, or progressive relaxation, which means that you just relax, and relax, and drift into trance gently and pleasantly.
Also you are fully aware, and in fact more aware of what is happening than you would be in normal circumstances, so the thought of someone else having control of your mind, is in fact purely comic book and film stuff. You can also come out at any time, should you so desire.