First, buy exercises and reference questions and do more. Practice makes perfect. This is a popular method, but it takes a lot of time and has a general effect, but it is essential. Second, in order to make the problems in the textbook transparent, we should draw inferences from one example and think of relevant variants. Many questions are distorted or complicated in teaching materials. This applies to everyone. Third, classify and summarize the questions you have done and heard, and clear your mind. This can not only avoid the futility of repeating questions, but also improve the efficiency of doing questions and answer them quickly.