Given the responsibility of the government for funding public education, the Office of the Governor of the State of Illinois commissioned the Illinois Workforce and Education Research Collaborative (IWERC) to explore how students were making postsecondary education decisions, including the relevant factors that influenced their general decision-making and their specific college choice. The Office of the Governor of the State of Illinois was also interested in understanding students' decisions to stay in or leave Illinois to pursue a 4-year degree, and the effects of the pandemic on college decision-making. To explore these matters, IWERC designed and implemented a survey for high school students in Illinois that asked students about the factors that influenced their decisions to pursue higher education after high school. A copy of the survey instrument can be found in the Appendix of this technical guide. This technical guide serves as a reference for all reports in the series (4-year college-going, 2-year college-going, decisions not to pursue higher education, and the effects of the COVID-19 pandemic on college decision-making processes). The technical guide is divided in two. First, the author presents a literature review of college decision-making nationally and, to the extent it exists, in Illinois. And second, the authors presents a methodological component, where an overview of the survey and the description of the sample of respondents are provided. The author also provides the limitations that the sample yields and explain why, while the findings are not necessarily representative of the state, IWERC can still make general conclusions about the factors that influence college decision-making for high school seniors in Illinois. The author also describes how to approach the descriptive analyses for this distinct sample, especially in terms of race/ethnicity and other self-reported categories. Finally, the author also presents the characteristics of each college-intending and non-intending group. The author also expands on the importance of intersectionality and the rationale to divide the same sample from different perspectives throughout the reports.