If you dream of going into the salon for a haircut, and in the dream your hair looks healthy and lovely and you are enjoying the experience, it is likely that the dream is an indicator that you are in a phase of positive change in your life, cutting off the "dead ends" so that something new and beautiful can grow in its place. Much like it is in real life, this type of dreamworld haircut can be a refreshing and optimistic sign (via DreamDictionary.org). 

If, however, you dream of someone cutting your hair off in a manner that feels threatening, hurtful, or against your will, or if you really hate the haircut and are feeling upset and regretful in your dream, this could represent feelings of being robbed of your power by either another person (do you know the person cutting your hair?) or by a situation you are experiencing in your life (via All Things Hair UK). Similarly, if you dream of cutting off someone else's hair (and you are not a hairstylist having a happy day's work), it could suggest you have a major bone to pick with someone.