The goal of Army instructors is to deliver the best possible instructional experience so students can increase their knowledge and transfer it to their duty positions. A major means of accomplishing this goal is to tailor training to the individual student, a concept espoused in the Army Learning Model. In order to tailor training, one must first identify the critical differences that distinguish individuals who are likely to have problems with course content vs. those who will not. One objective of ARI's tailored training research is to identify measures which predict student performance in a variety of courses with different student populations. In agreement with the research literature, relevant prior knowledge has been consistently found to be the best predictor of later performance. It was also determined that experienced instructors had a good understanding of what prior knowledge was relevant for their courses. The purpose of the guide documented in this report is to provide instructors the tools necessary for developing appropriate assessments of prior knowledge, to determine whether these assessments are a good predictor of course performance, and to show them how to apply prior knowledge and course performance data to identify the students who could benefit from tailored training.