Those who write historical fiction need to know the background of their characters. The detail they need to go into is not as much as the historian does, but, more than the romance novelist does, certainly.
When developing a story, involving a historical perspective, the writer/researcher must know what he is talking about. He can’t be found to be mistaken in a detail. If he is going to be using a character, or a scene, he is not thoroughly familiar with, a little study is in order.
First, he should consider what details the story contains that he is not familiar with. Is it a true character, the architecture, the style of clothes, or the food? You can’t have ice cream served at a dinner in the 1500s, unless the diners were rich and at the courts of France or Italy. Or perhaps they were in China 2000 years ago, where all such exciting things are invented!
A story about a noble woman in 12th century England would require knowledge of clothing, availability of dressmakers and secrets to beauty tricks from that time. For example, belladonna, a poison in some dosages, also can be used to dilate pupils, a very enticing look in women.
The story of the building of a church would require the author to know building techniques, origins of stone and transportation methods.
Those who include a real historical character in their stories should look for pictures, written descriptions and background material on the personality of the character. The further back in history, the fewer the number of people who have been written about. Writing about one of my characters from the 1600s, I can find little information about his relatives, but found that he was not honest in his dealings with others, having been pulled into court on a number of occasions for not paying debts. Maybe his relatives did not want to own up to knowing him.
All this research takes time. The internet is full of information and is the first choice I would make in looking for facts. Be flexible and precise in your use of key words and phrases. The internet gives instantaneous answers. Books give very detailed answers. Both may be needed to get the whole picture, depending on what you need.
For those who wish to write a story based on facts, the author needs to look at primary writings and, then, secondary writings. Read what happened before reading an analysis of what occurred. For example, do not read Shakespeare’s depiction of the assassination of Julius Caesar for facts. Shakespeare rearranged parts of the story to fit his narrative. “Et tu, Brutus?” never happened.
Whatever you do, do your research early. Your readers will appreciate the extra work.