It's common that, over time, the walls and floor of your pool may start to lose it's "like new" look. This is especially true if you don't get year round service, if your pool turns green, and/or your pool shell is exposed to the elements or some sort of staining material (organic or metal) for a period of time.
To return your pool to that "like new" look again, probably the best option for inground plaster based pool shells is to give it an acid wash. It should be noted that the process uses highly toxic and corrosive chemicals and can be dangerous, so it should be left to professionals. The end result, though, can be nothing less than miraculous!
Below is a portfolio of a recent pool refurbishing (70,000+ gallon condo pool) using the acid wash method!
(click image to enlarge)