What is the best treatment for a fractured skull?

Just time. Most skull fractures will heal in 3 months without any specific treatment. Some skull fractures that may require surgery include depressed fractures, fractures involving the frontal sinuses and compound skull fractures.
Depends. As long as it is not open or pressing brain, we normally observe the fracture, which should heal. If there is spinal fluid leakage into nose or ear, you might need specialist's evaluation. If it has opening of scalp, the wound needs to be carefully inspected and closed. If it has indentation into the brain, you might need surgery to prevent seizure.