Hi!!! Organic Chem section is actually is not that bad, they are like to ask questions concerning naming and isomers a lot, reactions are not that bad, the common ones, don't worry about it. Among sciences section the biology was the hardest for me, even though I love biology....
Flash cards. That's how I always learned them. You can go through a couple hundred cards in only an hour or two, and its a good way to 'stay sharp' by picking them up a few times and week and seeing how well you can run through them.
Draw an alkene in the middle of a page and arrows pointing away. Each arrow is a different reagent and it points to the product. One arrow for each reaction (Alkyl Halidehttp://www.cem.msu.edu/~reusch/VirtualText/alhalrx1.htm, Weak Acid, Oxy-Merc/DeMerc, ETC) You can do this for each chapter. As long as you note stereochemistry its a great way to sum up each chapter.