Start with history, add your five senses, and conclude with heart and mind.
That’s my formula for researching to write a historical novel, a genre that requires a combination of accuracy and inventiveness. In the case of my Ethan Gage novels, I have a fictional American interacting amusingly with famous real people but I have to make it convincing.
The Ethan Gage novels move sequentially in real time, meaning that unlike a James Bond or Sherlock Holmes tale, we know what year it is.