This chapter first throws light on the standard data file types with their usage, advantages, and disadvantages. In a digital library, data might be useless and considered incomplete without a metadata record. Therefore, the functions, uses, components, and importance of metadata are covered comprehensively, followed by steps to create quality metadata, common metadata standards available, different metadata repositories, common concerns, and solutions. The second part of the chapter focuses on the importance of the inclusion of optical character recognition (OCR) for digitized data, followed by different ways of getting data from (i) online repositories, (ii) relational databases, (iii) web APIs, and (iv) web/screen scraping to start a text mining project. Further, several online repositories, language corpora, and repositories with APIs available for text mining are enumerated. Finally, some of the essential applications of APIs for librarians and for what purpose librarians can use them in their day-to-day work are covered in this chapter.