You will just have to make your most reasonable guess as to where your ancestor is buried, go to the cemetery, and start searching the headstones. This project's aim is to list the transcriptions of gravestones from cemeteries throughout the nation. Once you have matched an ancestor with a graveyard, you need to seriously think about going to the cemetery itself. It just isn't enough to know where your ancestor was laid to rest. Getting there sounds easier than it often is, however.
Many cemeteries are easy to find, especially large ones that are listed in the phone book.
Often, the most difficult to find are family plots, plentiful in the eastern and southern regions of the United States. You may be able to get directions from funeral homes or the library. You've figured out where your ancestor is buried, and you have directions to the cemetery. You are prepared to go, like a good family historian should. Cemetery records may come to your rescue.