Hmm. I dabble in historical fiction so this is a problem I have to deal with. Personally, I read a lot of memoirs of people and can use how they reacted to events of history to fashion my character’s reaction to similar events. I believe this method to be the best but my knowledge is limited to the World Wars. Finding memoirs before that time period is more difficult.
The Devil saw me with my head down and got excited. Then I said Amen