Things To Explain First

These are good to explain to your subject before hypnotizing them. It will make it much easier.
Hypnosis is a naturally occurring state, it happens to you many times each day, it will probably feel very natural
Expect to feel relaxed, not necessarily "hypnotized"
You can't get stuck in trance any more than you could get stuck sleeping
In a trance your moral character and value system remain in place (you won't do anything against your morals)
In a trance you will most likely hear everything and be aware of things going on around you in the environment
Many people remember what goes on inside trance