Kids books about certain eras are a goldmine, since they include lots of weird daily life details.
Consider three areas that people will not allow screw-ups: i.e. guns, gowns, and horses for Victorian era.
For horses, making the horses get tired is pretty much gold for authenticity.
For Regency, Georgette Heyer is incredibly accurate for research, FYI.
If you change history, make sure that you specifically explain how it differs from reality, be very clear about changing history, and acknowledge in end-notes.
For basic source material, search for "Domestic Guides" etc.
If you're using a public domain character, if there's a big following, look for the Wiki.
If researching a historical individual through biography, try reading one contemporaneous and one written significantly later. And you're better doing a strong character, pushing a viewpoint, than going with the less offensive / more general speak-no-ill-of-the-dead version.
Don't get too stuck on trying to be fair, accurate, and covering everything. That usually results in less compelling stories.
When writing an outlier in a certain period, read historical things to learn where outliers *did* limit themselves to stay within societal norms.
If you're writing a public domain character, look for an annotated version of original source material to get good historical details.