A problem with using bookmarks is that you cannot readily see them in a document (even if they are displayed), and they are easily overwritten. You could use
http://www.gmayor.com/BookmarkandVariableEditor.htm as an aid to list them.
Other types of place marker are more robust. For example you could use content controls, which can be protected from accidental deletion, or you could use document variables.
Whichever you use, create a template rather than a document as the new documents created from it will always have the bookmarks/variables/content controls that you put in it, even if the user screws up the document.