Spread the Wealth
As mentioned earlier, a “cluster” approach to family history research requires you to branch out your genealogy search to include records of neighbors, family friends, or other individuals with whom your ancestors interacted in some fashion. Certified genealogist Elizabeth Shown Mills memorably refers to this group of individuals as your ancestor's “FAN club” (Friends, Associates, and Neighbors). Cluster genealogy is generally used as a workaround approach when records on your own ancestors are lacking, but some people actually choose to focus their research on a group of unrelated but connected people, such as members of a particular town or school.
In its most simple form, cluster genealogy might mean ordering the death certificate for each of your grandmother's siblings when her death certificate turns up with “unknown” in the blank for mother's maiden name. The hope is that at least one of the siblings' informants knew the mother's maiden name and ensured that it was recorded correctly on their death certificate.
A cluster approach is frequently used to track down the family of a female ancestor. Individuals usually married someone who lived nearby, or was otherwise in their social circle, such as the sibling of a classmate. Expand your research to include the records for individuals named as witnesses on your ancestor's land deeds or neighbors identified through census or tax lists and you just might identify your great-great-grandmother's family!
Another, slightly more complex, example of the cluster approach is acquiring copies of and platting the land grants for all of the individuals who owned land in the vicinity of your North Carolina ancestor around 1725 in an effort to distinguish him from another man of the same name who also owned land in the area.
The next time a previously unknown name pops up in a record that relates to your ancestor, spend some time researching him or her. At the very least, be sure to record the name in your research notes in case it pops up again. There may just be a connection there!