First, study theoretical books and seek information from theoretical classics;

The second is to learn from other people's theoretical research-you can check the knowledge network (ki. net/);

Third, browse some materials of recent annual meetings and forums of research topics, representing the academic frontier trends.

One thing needs to be explained: when learning other people's theoretical articles, we must pay attention to which books and papers are cited by others and learn to find more things we need. In this way, with the deepening of research and study, you will master more and more information and find systematic clues from it.

Wish you success! !