This guide focuses specifically on data from the data provider and company, Altmetric, but other types of altmetrics are mentioned and occasionally used as a comparison in this guide, such as the Open Syllabus database to find the educational engagement with scholarly outputs. This guide opens with an introduction followed by an overview of Altmetric and the Altmetric Attention Score, Altmetrics and Responsible Research Assessment, Output Types Tracked by Altmetric, and the Altmetric Sources of Attention, which include: News and Mainstream Media, Social Media (X (formerly Twitter), Facebook, Reddit, and historical data from Google+, Pinterest, LinkedIn, and Sina Weibo); Patents, Peer Review, Syllabi (historical data only), Multimedia, Public Policy Documents, Wikipedia, Research Highlights, Reference Managers, and Blogs; finally, there is a conclusion, a list of related resources and readings, two appendices, and references. This guide is intended for use by librarians, practitioners, funders, and other users of Altmetric data or those who are interested in incorporating altmetrics into their bibliometric practice and/or research analytics. It can also help researchers who are going up for annual evaluations and promotion and tenure reviews, who can use the data in informed and practical applications. It can also be a useful reference guide for research managers and university administrators who want to understand the broader online engagement with research publications beyond traditional scholarly citations, also known as bibliometrics, but who also want to avoid misusing, misinterpreting, or abusing Altmetric data when making decisions, creating policies, and evaluating faculty members and researchers at their institutions.