Genealogists are human. We forget.
No matter how much we know about record access, record interpretation, record creation, the law, human behavior, culture, customs, etc. there’s always something the researcher can forget.
I suppose admitting to that isn’t good for my overall reputation, but here goes.
What I forget more than anything is “the frequency with which some families move.”
A family I’m still working on was in Clinton County, Illinois, in the mid-1840s. I looked for them in the 1840 and 1850 census indexes there with no success. Manual searches did not help either. Looking for them in 1860 was just as unsuccessful. The short version of the story is that apparently the family was there for a few years in the mid-to-late 1840s and probably moved shortly before the 1850 census enumeration.
The ease with which I sometimes forget about the “movers” is partially due to my own family background–they tended to stay in one place for longer periods of time. I have my share of movers, but they usually hung around an area for at least ten years before moving on.
The point here is not that people move–they do. The point is that many times how we approach research can be colored by our own experience with our own families–or the ones that we researched first and were easiest to find. The approach that worked with those families might not work with other families, other time periods, or other locations.
Don’t let what worked with families before prevent you from having success with new ones you start to work on.
Get outside your usual genealogical process path and ask yourself:
What am I assuming about this family that may not be true? How might this family be different from others I have worked on before?