Hypnosis is perfectly safe because you are always in control.  At any time a person may quickly and easily come out of trance if they wish.  However, if you are under the care of a psychiatrist or doctor, it is always recommended to check with them first before scheduling hypnosis.  Hypnosis is not a substitute for medical or psychiatric treatment.

If you have ever become so engrossed in a movie that you didn't notice how much time passed, then you have been hypnotized.  So basically, yes, most everyone can be hypnotized.

There are varying depths of hypnosis.  Different people may experience different levels of hypnosis.  Even a light state of hypnosis is effective because the subconscious is just beneath the surface of everyday consciousness and easily accessed.  You can have meaningful experiences at all levels.

Hypnosis can feel different for everybody.  Possible body responses are relaxation, heavyness, floating, or expansion.  Mental responses could be calm, focused, peaceful, insightful.  Emotions may also come up.  Hypnosis can be experienced with any of the senses: imagery, sounds, smells, sensations, and even tastes.  Some report a sense of time distortion.  However you experience hypnosis is right for you and will be supported by the hypnotist.