Every cemetery has their own rules; follow them.
Always record females using their maiden names.
Be sure to check for a town or county historical society in the area you are researching. Know their hours of operation and their visitor rules.
The National Archives and Records Administration (NARA) in Washington, DC and its Regional Branches, is the principal repository for records relating to the US federal government. These include the original paper copies of the federal census, all pre-World War I military records, Native American records, military service and pension records, naturalization records, ship passenger lists, land-entry case files, and homestead and bounty land warrant records. NARA's website is the place to begin research for federal records.
A census is an official counting of the population living in a given locality on a designated day set at intervals. The census places an ancestor in a specific place at a specific time.