Suggestions for researchers who want to contact the experts?

I'm working on my first historical fiction novel. It seems that no matter how many dozens of books I read on the subject, there are always day-to-day details of the time period that I can't quite figure out. It's time to start reaching out to the experts: archivists, professors, historical societies, etc.

I'm planning to just dive right in, but should anyone have helpful suggestions or words of warning, please don't hesitate to share.

My one burning question is how best to introduce myself.
Do people often react poorly to "I'm writing a novel, and..."?

Suggestions for researchers who want to contact the experts?