The trouble with research is that it’s kind of addictive.
The trouble with Google is that it panders to that addiction.
So you need to find ways to keep more or less on track when you do this.
First of all: write down the exact question you are looking for an answer to. “All about the fourteenth century” is not the best place to start.
If you are world-building from scratch, then at least try making some headings like “Food”, “Architecture – elite”, “Architecture – Peasant”, “Transportation” and so on. Then start with one, and try really hard to follow it through till you feel you have a handle on that section before starting on the next one. Keep some paper and a pen beside you to write down any off-topic stuff that comes up as you do the research – but don’t abandon the original search.
For example: You are looking for information about food, and up pops a website about “medicinal plants”. Oh! You think. I need to know about those, too.
DO NOT suddenly start following that line of research.
Make a note, or add it to the list of the topics you’ve already got going.
Because if you click on that site at 9 am, I guarantee that with the best will in the world, you will suddenly realize around midnight that you now are looking at “Common poisons of 12th century Scotland”, and that your list of Foods of the 14th century still only consists of “bread, porridge”.
Try to remain focused on one topic/subject at a time. Really, really try.
Another way to tackle things is to open a .doc called “Additional Stuff” and every time you find a site that is only a bit off-topic, go to it just long enough to copy the URL onto the word.doc. I like to organize my stuff into folders and subfolders anyway, so I wind up with a folder labeled 14th Century, and then a folder called “Food”, one called “Architecture”, and so on. Inside each of those will eventually be word.docs called “Notes on xxx” and “list of related sites on xxxx” and stuff like that.
(I also have a notebook filled with questions that need to be resolved, and bits of other stray info I come across, because I’m not always handy to the computer.)
It used to have to all be on those little index cards, and inevitably I would lose some of those, because, yes, I am feckless. Organized, but irresponsible, that would be a pretty good summation of me, in general.
It seems a bit time-consuming, I know, but later on, when you start to describe a banquet scene, and you go looking at those files, that list of related sites will remind you that there was, literally, an extant menu of a feast hosted by Henri de Valois, and you have the link right there, and hey! Presto!, There’s all the information you need.
And you didn’t have to stay up past midnight even once.
One other important reminder: you are not obligated to read every article you come across, in total, before deciding that it is useful. This is especially true of academic articles, and the rule of thumb here is to read the abstract (to make sure that the paper actually treats the subject you are researching) and then scroll down to the “Conclusion” and read that to make sure it actually went where it said it was going. Only after that will it become potentially necessary to wade through the background literature summation, the methodology, the data, and the discussion of said data.
Trust me. It’s how everyone gets through grad school before their eightieth birthday.