In text, refer to homeowners by their first names after first reference. For architects, designers, and other professionals, after first reference use last name only—unless they are also the homeowners!
BH&G: Homeowner and subject, use first names on second reference. Professionals use last name on second reference. (Changed 7/5/2017)
The first mention in text, captions, and sidebars should identify homeowners and professionals with their first and last names.
In general, don’t use last names for minors; last names may be implied, however, if children are part of a family featured in a story. If using a minor’s last name is important to a story (a 14-year-old recipe-contest winner, for example), verify that the minor’s guardians have signed the proper release form(s).
See also the Quotes and Quotation Marks section of the BHGStylebook.