The document discusses revision techniques for learning and their effectiveness. It finds that some techniques have low impact and result in little recall, some have moderate impact, and some are high impact. High impact strategies include practice testing oneself using flashcards or a Leitner box system, and distributed practice that spreads studying out over time. The Leitner box approach involves categorizing cards into piles based on confidence level and prioritizing time spent on less confident areas. Examples of how to create effective flashcards are also provided.