While recall and precision are two popular performance indicators in information retrieval, search engineers are usually are not really aware of them in their daily work. You can, however, find clues to improve search user experiences by re-examining these two indicators. This presentation will show you the process of improving information retrieval performance using these indicators. As the means of realizing performance improvement, this presentation will include demonstrations of utilizing corpus—such as repositories of business documents—and learning-to-rank in practice to explain the process using NLP4L.