Organic chemistry is definitely not something you can just cram overnight. It can be really dry. So, to memorize all the relationships between chemical groups, types of reactions, and the corresponding reagents and conditions, I made a color-coded mindmap. Feel free to use mine as a basis of how to contract yours but I recommend trying to construct one by yourself. Draw the mindmap as many times as you can without reference until you get it totally correct. This will be extremely helpful for those long (and heavy mark weightage) structure elucidation questions and those simple (unless you forget) reagents and conditions questions.