Schools and school districts are data-rich environments, with heaps of data on student demographics, achievement, outcomes, and perceptions. With so much data available, it can be easy to get caught up in the sheer enormity of the data sets. A cohesive data analysis and decision-making process can help schools, districts, and additional stakeholders to ask good questions, sort through the available data, identify which figures are needed to answer the questions at hand, analyze the data, and, ultimately, use the information gained from the analysis to make good decisions and carry out meaningful action for school improvement. Data can provide policymakers with objective information needed to make decisions about their education systems, provide states with information about program effectiveness, and provide schools and districts with information about student learning to influence instruction, programming, and teacher professional development. With recent changes in accountability expectations of educational institutions and an increased awareness of the power of data, both schools and districts are expected to be data-driven organizations, making decisions and taking action based on the facts presented to them through data. This is a considerable charge, but one that can lead to powerful improvements in student achievement. The goal of this guidebook is to build capacity for data use at the school, district, and state levels. Ideally, data users will train their colleagues on the data inquiry process, building an entire system of educators who are comfortable with and skilled at using data to take action for school improvement. This guidebook contains the following sections: (1) Background Information; (2) Data Team Logistics; (3) Data Inquiry Toolkit; and (4) Sample Data. The Data Inquiry Toolkit and Sample Data sections walk the user through each step of the data analysis and decision-making process. The following appendices are included: (1) Glossary; (2) Question Bank; (3) Color-Coding the Data; and (4) Creating Visual Displays of the Data. [For "Using Data to Guide Action for School Improvement: Facilitator's Guide," see ED565721.]