Historical writing evolves. So there are some things that a budding historian should not say, do, or be. I’ll start with words that have gone out of fashion.
“Dark Ages” was a pejorative term historians used (until recently) to describe Europe beginning around 500. Influenced by the Enlightenment, these nineteenth- and twentieth-century historians thought that after Rome “fell” (another term going out of style), Europe had plunged into a benighted age of deteriorating trade, economic stagnation, and ignorance. Europe didn’t get fully back on track until the rediscovery of the ancient civilizations—the Renaissance. The first 500 hundred years were the worst, thus the Dark Ages.
That prejudice is gone. The Middle Ages as a whole are seen as a period of commercial and agricultural vitality. The “fall of Rome” has given way to “late antiquity,” and the “Dark Ages” are now the Early Middle Ages (followed, at least among Anglophone writers) by the High and Late Middle Ages. (By the way, notice that I said “Anglophone,” not “English-speaking.” Trying to sound like an academic.)