First, the problem is manifested by a special aspect.
Second, limit the topic to a specific time range.
Third, look at this problem from a special event.
Fourth, discuss the above three factors together.
For example, we should study the ethnic minorities in Taiwan Province Province. When considering the first factor, we can discuss the status of chiefs or women among ethnic minorities in Taiwan Province Province, or their integration with their compatriots in the plains, or how their costumes are different from those of Filipino aborigines, so that the big topic can be narrowed down to a smaller level.
When discussing the second factor, we can study the living conditions of ethnic minorities in Taiwan Province Province during the Japanese occupation.
From the third angle, we can discuss the role played by ethnic minorities in Taiwan Province Province in the Wushe incident.
The fourth scope can describe the changes in the economic life of ethnic minorities in Taiwan Province Province after the retrocession.
The above four methods can narrow the limitation of a big topic to a certain level or even a certain range for specific research. If we can learn something from it, this paper will be very valuable. (Academic Hall provides more paper knowledge)