One of the long-term "resource" projects that I'm gradually collecting data for is a catalog of romantic, erotic, and sexual behaviors indexed to the cultures and eras when they were popular, and placed in their social context. Think about the simple kiss. What did kissing mean in a given culture? Who kissed whom? In what context? What was communicated between the people who kissed? How as that kiss interpreted by those who witnessed it? If you're writing a sapphic historical romance, under what circumstances might ytour characters kiss? Will their first kiss be erotic or social?