There is always something more to read which can potentially give you more insights on your topic. 

You will never reach a point that will tell you you're done.

Since, research is open-ended, it can be hard to keep up.

Thus, it is better to decide before...

These are some of the essential things you should know:

• Sci-Hub is helpful to get access to papers. Alternatively, emailing authors can give you access to papers, but it tends to slow reading down.
• Google Books can help you find specifics in a ...

A major problem while doing research is that we tend to forget what we've read or where did you read it. 

1. Some people use Zettlekasten which is a note-taking system.
2. Another system is Caplan's approach, where you highlight the sections...

Once you've found the right keywords & some main papers, try to find reviews.

• Literature reviews qualitatively review all the papers on a topic.
• Meta-analyses try to collect effects from multiple papers on the topic to give a quantitative answe...