I'm talking out of my ass here, because I'm a master procrastinator, but you know, I try to follow these.
Healthy or not, I'm going to second caffiene. I also recommend writing down a time you're going to study on paper or in your notes. Then when the time comes, sit down with your material and set a five minute timer. Gradually increase the amount, but by completing x time, it can add a sense of accomplishment. It doesn't always work, but sometimes the problem is just starting. Another thing I've learned is have a reward in mind. For example, if you study for 15-30 minutes, then you can do something you enjoy for 15-30 minutes later.