Stephen LaBerge and Howard Rheingold introduced the concept of Dreamsigns in the 1990 book "Exploring the World of Lucid Dreaming." In short, a Dreamsign (all one word) is "a peculiar event or object in a dream that can be used as an indicator that you are dreaming." The idea is that if you can familiarize yourself with your personal Dreamsigns, you will more likely recognize them in your dreams and become lucid. In the book, they propose a somewhat complicated system for categorizing and inventorying your own personal Dreamsigns. I have always found this concept intriguing, but too laborious to be practical. However, recently I was reviewing the research that went into creating their categorization system (in Lynne Levitan's 1992 article "A thousand and one nights of exploring lucid dreaming") and noticed an interesting bit of information. The two most common Dreamsigns (and with high likelihood of triggering lucidity) were: 1) "Dreamer does something unlikely or impossible in waking life" and 2) "Dreamer experiences unusually intense emotions." Thus, I would propose that a simplified version of Dreamsign familiarity/recognition would be to focus on just these two categories. So, focusing on Dreamsigns like flying or intense surprise/happiness/fear might give you more "bang for your buck" and may not require such intensive analysis of your dream diaries.