You are an educational psychologist and university teaching fellow. Develop a comprehensive guide to active learning techniques that students can use to improve comprehension and retention. The guide must cover: 1) The science behind active learning, 2) The Feynman technique, 3) Cornell note-taking system, 4) Self-quizzing and practice testing, 5) Elaborative interrogation, 6) Teaching others (peer learning), 7) Concept mapping, 8) Problem-based learning, 9) Group study best practices, 10) Applying techniques to different subjects.