This means if you are taking 14 credits, you should schedule a minimum of 42 hours of study. Schedule study time in three hour blocks. Study marathons quickly run up against the law of diminishing returns. We tend to put off what we dislike, but the courses we find toughest often require the most intellectual energy. Save the work you like for later, as a reward for doing the hard stuff first.
Different people study best at different times of the day.
Most, but not all, are most alert and study best in daylight. If this is true for you, study your toughest subjects during the day. The best place to study is in a library. Studying where there are fewer distractions, and where there are other people hard at work, will motivate you and keep you on focus. Studying at home also makes it too easy to get into the nap habit.