1. If readers can give relatively more search terms when searching for a single book, the fewer search terms appear, the greater the probability of finding the required book.

2. If readers want to find a large category of books, for example, some readers want to know the history of China. In this case, just type "China" and (and) "History" in the free search field of OPAC, so that the required bibliography can appear in the smallest scope. If readers only type "China history" in one column, then both "China" and "history" will appear, for example, China economy, China culture, American history and so on. Content that has nothing to do with readers' expectations will also appear. Or there is a simple retrieval method: classified retrieval. Readers can directly find the item "History of China" through the classification of their library, and then use the corresponding library book number to refer to specific books.

3. Using OPAC to search, the most commonly used search method is "subject words". Because "subject words" are standardized natural languages, they can generally reveal the central meaning of literature information. Without knowing the title and author of the bibliography to be searched, the recall rate can be improved by using the subject words to search.