which is more effective?

i think it is more effective if you study and understand what you have studied more deeply. it is a matter of understanding the lesson of what you have read. studying fast may be good as long as you understand all you have studied.

One should pay serious attention to his or her studies. It doesn't matter if you memorized all the facts and information the teacher had given to you, what matter is you know well what are you studying. Paying attention more on details will help you to understand more important and bigger information. Studying by mind and also by heart is a good thing. It helps a student not just to learn but also to enjoy what he or she is learning.It is also important to always pray and ask God for His guidance.

for taking time to study and having ample time to revise my work is more effective than cramming in the last minute, though sometimes I tend to do this when I have a lot of things in my hand.

Spending more time studying is better. I find when I cram, although i remember what I learned at the time of the cramming and an hour later. but the moment i am sitting in front of the test I forgot everything I learned. So slow and steady is the way to do it, I'm trying to do that