Just as there is no single key to open all locks, there is no single surgery for all scars. There are books not chapters so it is not possible to explain in a few lines. Best is to visit an expert experienced plastic surgeon. He will examine your scar, surrounding area and based on your expectations he will suggest what would be best for you.
Steroid injections for Keloid and hypertrophic scars, Z-plasty, M-plasty, local flaps like Limberg or tissue expansion for contractures, flap surgery and skin grafting are just to name a few options for scars.