Just start doing it and keep at it! You need to have a structured plan and your days need to be planned out. The pomodoro technique has proven very effective for me:
http://cirillocompany.de/pages/pomodoro-technique
Study in 1-hour iterations, take 10 minute breaks. Repeat until the sky is pitch dark.
This works for me because I feel reassured of how much time I'm spending on studying, how much time is going by and so on. I also have the motivation to challenge my timer and do as many things as I can in that one hour.
A successful doctor once told me: "The brain needs at least 20 minutes to start focusing on something. If you interrupt your brain in the midst of this, you will lose focus and thus lose productivity. Don't take breaks after an hour, but maybe after 12 hours. That's how I studied for my medical exams".
I'll leave this with a great quote:
"It's better to suffer 5 years and profit 40 than profit 5 and suffer 40".