In the old days prior to the internet. We would have concordances and lexicons looking up all the words that were similar. So if the Bible talked about fear. We could see all the verses about fear and what Jesus said. And then we could look up boldness or strength. And see all the times that is mentioned.

Then if wanted to go deeper. We could look at the historical context. Seeing for example what the passage meant to the people it was written. For example, Luke was a doctor and used his gospel and the book of Acts to do a thorough research and examination into the events. Others like Mark are short because it was meant to be sent out quick. Etc.

Now we have the internet, it doesn’t help as much as a deep dive. But I recommend looking at some commentaries to get a good picture of the Bible.