Comfort = Comprehension

Be Comfortable (and Awake).

That's probably one of the most distracting things for me personally.

Studying at 4am, over a cup of coffee with a drill instructor yelling in your ear... OK, I do that some times, but a review of material and actual studying of it are completely different. A few hints to be productive:

-Take a quick shower. No, does not have to be cold.
-After an hour of studying do 10 push-ups. (women can do some other physical exercise)

Now, as far as comfort:
- Stay warm.
- Have adequate light.
- Reduce outside distractions (ex: cat, dog, noise from your cell phone charger making low buzzing sounds)