To make the most out of the second opinion you are getting from a doctor, request a full set of medical records from your first doctor, including any x-rays and MRI reports and preferably images (on a CD) or films and show all the materials to that subsequent doctor. The more information the second doctor has, who has never treated or evaluated you before, the more likely he is to give you the best and the most complete advice.
Even if you don't have health insurance or your health insurance doesn't cover getting this kind of second opinion, it would be well worth paying the second doctor for a couple of hours of his work in order to determine whether you truly need that surgery. This is especially true if you are considering having a serious surgery, such as back, shoulder, or knee surgery, which may involve serious risks and side effects.