If your upcoming exam is comprised of 10 chapters that were 25 pages long, then an easy review session the night before is not the way to go. It is super easy to get distracted on your own, making the information difficult stick in your brain properly. Scheduled breaks keep getting longer and longer, and sometimes you just want to talk it out with someone who gets the material -- not your dog.
This is why having a friend in your classes to study with creates the best results. Not only do you have different notes, making it easier to gather all the information needed for the exam, but you can also split up making the study guide. And the best part is not having to worry about not making any sense when trying to grasp a concept. You can make hysterical analogies that will be ingrained in your head forever, because you and your best friend laughed for hours when you came up with them. It's the moments like those that are what helps ignite your memory during an examination.
In continuum, the study breaks are 20 times more fun with friends, and always involve food. Loading up on candy and other sugary substances to keep you awake all night is the best part. The material you are studying is always more interesting and fun to learn when you have someone like your best friend to learn it with you. When the night is getting late (or shall I say, when the morning is beginning), the delirium creates even more jokes, but you have your best friend to push you to stay awake and chisel as much information into your head as possible. You don't want each other to fail, and that is the best part -- you won't let each other.
You have so much more motivation when studying with your best friend because it feels like you are taking on this exam -- basically, the apocalypse -- together. This collectivity leads to the best results: an A.