It is important to remember that not all your ancestors may have grave markers. Many times a simple boulder or wooden cross was used to mark the grave. Some grave markers were made from materials that were not meant to last; and, unfortunately, many grave markers have been dug up over the years for agriculture, development, logging and various other reasons. Some may not have recognized that they were digging around a grave. In other cases, grave markers may end up in yards, as foundation stones, or as rock walks.
After the 1850s, it seems to get easier to find graves in the United States, at least in the states that were settled by then. You may be fortunate and have a source in your family who remembers an "old family cemetery." A Family Bible may be around that tells when and where your ancestors died and were buried. Funeral cards became quite popular during those years. You can find over 22,000 funeral cards listed on the Genealogy Today web site. Obituaries may be in the newspapers. After the 1920s, death certificates may provide some clues on burial.
Before the 1850s, searching for graves becomes more problematic. If you know where your ancestor lived, it is probable that he or she is buried in that place. The shipment of bodies to other locations was not a common occurrence until the Civil War, 1861-1865.
One source to help locate cemeteries or obtain records is "Cemeteries of the U.S.: A Guide to Contact Information for U.S. Cemeteries and Their Records," edited by Deborah M. Burek. Another source is Interment.net although not all counties are listed for each state.
For state listings, some states guides have been published. A few include "Cemetery Locations in Wisconsin," by Linda M. Herrick, and "Missouri Cemetery Inscription Sources: Print and Microforms," by Elizabeth Gorrell Kot and Shirley P. Thomson. Neither of these books are for sale on Amazon.com, so it will be necessary to check your local genealogical library or www.worldcat.com Jeanette Holland Austin's "30,638 Burials in Georgia" is another example of a great resource that may list your ancestor's grave -- or not. Her book is currently available on Amazon.com, but is also found in many genealogical libraries.
Another important avenue for locating your ancestor's burial place is to search county, local and family histories. These publications often provide a treasure trove of information for the genealogist. Always remember that the information entered into county histories may not be entirely accurate, but there is a grain of truth in all family stories and traditions.
You may be reading one of the family stories in the county and see where it says that your ancestor left Calhoun County, Georgia, and traveled to Chicot County, Arkansas. Often county and family history books may state that the ancestor was buried in the garden.
One of the great services of county histories is that they usually list cemeteries in the county. These lists may be quite exhaustive or not large at all. It may help you to look through the lists. Often the names of the people in the cemeteries are not indexed because they are already alphabetical in order. Sometimes county and local histories will list older cemeteries that may have been destroyed in the intervening years. That is unfortunate, but it is a frequent occurrence. In the Randolph County, Georgia, History, Vol. II, cemeteries that can no longer be found are mentioned. A concerted effort was made in the 1950s to go out in the county to document the graves. Oral histories and traditions are all that are left of those graves, but at least the book provides a clue to descendant's looking for that link.
Another place to check for county cemeteries is on www.rootsweb.com and www.usgenweb.com. Look first under the state resources then go to the county level. Some counties have a large number of digitalized records while others do not. If you are fortunate, someone will have recorded your ancestor's grave. These sites often list local cemetery books that may have been published by a local historical or genealogical society. If you have the title, you can go to www.worldcat.com to see what libraries own the book.
It is also a good idea to check the Family History Library Card Catalog to see if your family history is online. Enter in your family name and start searching to see if anything has been published about your family. Some published family histories may also be available at www.genealogylibrary.com (a fee-based site).
These suggestions are meant to get you started in your search for ancestor's graves. Remember that it may take a long time to locate the burial site, but it will be well worth the search.