One good method which hypnotist used to find out if a person is a good subject for hypnosis is the use of hand clasp exercise.
Simply ask the group to take a few deep breath and follow the instruction. They are to clasp their hand tightly together while you give suggestion that when they try to pull apart, they can’t do so because the hands stick like glue.
There will be people who break away the hand clasp despite the suggestions. These people do not make good candidate for hypnosis.