I found this interesting quote from the following book:
Fudge, George H, and Frank Smith. LDS Genealogist’s Handbook: Modern Procedures and Systems,. Salt Lake City: Bookcraft, 1972, Page 121.
Intelligent research cannot be conducted without some knowledge of the economic, social, religious, and historical background of the country whose records are being searched. For instance, events in these categories affect the movement of people and the direction of that movement. The keeping of records was affected by wars and by the formation of new religious sects.
There have been promotions by genealogical companies in the past few years that have maintained that you don't have to be a genealogist to do family history. Well, one problem with this statement is that by definition, if you are involved in family history, you are a genealogist. The definition of a genealogist is so vague as to include all possible levels of involvement in family history. Here is the most common definition found on the internet in a number of websites:
A genealogist is "a person who traces or studies the descent of persons or families."
Perhaps we can find another more restrictive definition that will support the idea that doing family history does not involve genealogy? Here is a common definition of "genealogy" from the Britannica.com website:
Genealogy, the study of family origins and history. Genealogists compile lists of ancestors, which they arrange in pedigree charts or other written forms. The word genealogy comes from two Greek words—one meaning “race” or “family” and the other “theory” or “science.” Thus is derived “to trace ancestry,” the science of studying family history. The term pedigree comes from the Latin pes (“foot”) and grus (“crane”) and is derived from a sign resembling a crane’s foot, used to indicate lines of descent in early west European genealogies.
As I have written in the past, the term "family history" was coined to avoid using the word "genealogy" to avoid all those people out there who are allergic to genealogy.
I certainly agree with the first quote above about the need to know a lot about everything to do an adequate job of genealogical research. I frequently find that I have to do research about my research to understand what my research has found. Just today, I tried to answer what I thought was a simple question and ended up spending a great deal of time researching online and never did get the original question answered.
I guess the real message that genealogists need to convey is that genealogy is a really hard, complex pursuit, and doing genealogical research is not easy. One of the possible reasons why genealogy is not a generally accepted academic subject is that is so broad and so difficult only a handful of people can possibly master it and even then there are very few paying jobs available for "professionals."
The best answer to the question in the title of this post is that you need to know how to do research; real difficult research in libraries, archives, online, and sometimes standing in a cemetery.