Most of the following, you don't actually need to do, but if you think carefully, you will realize there must be some objects, some cherished possessions, some daily routine that will show up in your story. The time to research them or organize what you know is now, not while you're trying to crank 50,000 words.

So, the following isn't a list of what you must do, but of things you might need to do. Whether they are important depends on the nature of your story. But something along the lines of the following will exist for your story.

If it's historical fiction, then one thing very important for maintaining your setting is everyday items and everyday tasks. Even if you feel you have it down by heart, start writing out how a character (your main character or someone else) goes about their ordinary day. How do they rise, have breakfast, go about their occupation or their household chores. Do they have any animals? How are they kept, fed, whatever.

Break it into a list. Suppose they're a farmer. What's a medieval Irish rake like? Does a fellow farmhand pull the plough or does a beast of burden?

How are they clothed? Do their garments close with buttons, hooks, ties, cords? What color? What material?

Where do they get water? Food? Other essentials?

Or at night time, how do they light things? Lamps? Candles? Just the fire in the hearth? I can tell you this particular question is heavily dependent on what their station in life is. Candles and lamp oil cost money.

Are they literate? If so, what written material do they have in their possession or have access to? Is the cover brown, black? Is it a scroll or a codex? I can go on, but it would get silly.

...
Regards,
Eric Fretheim
Assistant Prep Leader, 2015 October NaNoWriMo Prep Challenge

"It is perfectly okay to write garbage-- as long as you edit brilliantly." ~C.J. Cherryh

“No, writing 50,000 words in a month is normal. You are not crazy. This is not insane.” ~Teri Brown