Sometimes I think tracking ancestors back to their country of origin is sufficient. This is especially the case when ancestors arrived in America early, say during the 1600s. At that point in history you are dealing with England, Wales, Scotland, Ireland, The Netherlands, Flanders, regions of France that were predominantly Protestant, Switzerland, and various German States. There were a few from other parts of Europe, indentured servants and slaves from West Africa, and a handful of other places.
My focus here is on the British Isles. With immigrant families arriving before 1650, tracing those families back can be tricky and frustrating. I am currently working on three families [Jermy, Coningsby and Boteler] and a fourth [Meautis] already posted.
In time, we are looking at roughly 1066 to the early 1600s. Patronymics were predominate in many places [Wales and The Netherlands, for example] Place names and occupational names were frequent. Spelling was relatively unimportant to the surname, since many were illiterate or semi-literate. "Final spelling" of surnames was 300-400 years away - no matter what your great-aunt said about the spelling of your surname! Latin, Old English, French, German and other spelling variations might have popped up.
The names of females in the family were not recorded with the accuracy of males. You might find a wife listed as "daughter of ______" more often than not. Likewise, you may only get a given name; a problem that has stayed with us well into the 19th century.
Sorting out which of three wives your 7x great-grandfather belonged to could also be an issue. Males and female given names tended to be very repetitive: Thomas, John, William, Henry, Elizabeth, Margaret, Mary, Anne, etc. Sorting out four John LeSeurs born between 1350 and 1360 to three Thomas LeSeurs and one William LeSeur, can be a challenge.
One ancestor may have been of major importance in the parish, town or shire. His son left little or no mark. That can compound the situation.
Poor record keeping can play a role in tracing ancestors. Sometimes you are more likely to find a burial only. Marriages can be misleading. An ancestor might have married at 14, 15 or younger back in the 1300s. You have to know your customs and geography. Marriages were likely to be about joining families, lands or alliances rather than romance. Boy marries girl two farms over wasn't so common before the 1600s.
Then there are the researchers. Mr. Smith may have one slant on the family, while Professor Jones has another and Ms. Hall, PhD yet another.
Sometimes just knowing that your Virginia ancestors were Huguenots and arrived from Calais about 1680 is enough. Then again, there's the hunt to find out more. Curse you genealogy!