During my vocal coaching lessons I teach a variety of exercises to improve range, technique, breathing etc. (see the Vocal Coaching page for examples)
Any exercise can be overworked or misused so that it will do you more harm than good. You don’t develop your voice by pushing it to it’s limits. You will develop your voice gradually by training it to work efficiently with balanced coordination.
It is important that each exercise is done correctly and with patience, there is no quick fix!