Hi Miguel, this is such a great question!
For me, studying starts by making sure I have eaten a healthy meal (no carbo-loading! It will slow you down and make you feel sleepy), and that I have a designated area to study, that is free of as many distractions as possible. When I'm at home, I make sure to move to the dining table, or office area (no studying in bed!), and when I was at school, I picked a cube or table area that was more remote and away from a lot of people, and when at work, I choose a conference room and sit with my back towards the door or window. Keep some healthy snacks to munch on, and a water bottle handy.
Next, I get organized. Take a few minutes to write down what you need to work on, and in what order. If you can, print out the material, rather than working on your laptop (it's too easy to quickly surf to the Internet and more). Switch your phone to totally silent and place it in your bag - try to avoid getting distracted by texts or phone calls. Lastly, close your eyes, and take a few deep breaths to get centered, and begin.
As you are studying, write things down, make flash cards, highlight, etc. I have found that writing down what I need to memorize helps it to "stick" in my brain. When I was in law school, I had a 26 page typed outline, that I re-wrote by hand, two times, to get the information to stick. By the way, I prefer not to study with music, but if you find that it helps you focus, I say go for it!
Remember to take breaks! This is so important. Get up, stretch, take the long route to the bathroom, run up and down the stairs. You need to rest your eyes and your brain. It doesn't matter if your break is 5 minutes or 15 minutes, it will help you. As you accomplish one task, cross it off, and congratulate yourself before beginning the next one.
Lastly, don't think you need to spend 12 hours studying. Your brain needs rest. Find a time that works for you (for me, the mornings were better than the evenings). When you are done studying (and you will know - you won't be able to study any more) close the books, and head home to do something to relax. I would go to the gym for a little bit, and then watch a funny tv show such as The Office. Get good sleep, and get ready to study again the next day.