This document provides an introduction to using Twitter for activism and political organizing. It begins with an overview of what Twitter is and some key terms. It then discusses five examples of how Twitter has been used for activism: 1) Spreading news and information quickly, using the assassination of Benazir Bhutto as a case study. 2) Running social media campaigns to draw attention to issues, using examples from the US. 3) Coordinating collective action in emergencies, using wildfires in San Diego. 4) Crowdsourcing solutions, using the example of a Twitter search engine prototype. 5) Maintaining personal security for activists, using examples from Egypt. The document concludes with steps for organizing an activism campaign on Twitter