This is what i do and it has helped me so far:

- before starting to study, I make up mind to finish X number of chapters in Y hours
- keep a big tumbler full of water on my table (helps keep me awake and active)
- turn the music on (might be a distraction for some, but it helps me instead)
- start studying (i often write something important on a scratch paper - helps remember + avoid boredom)

i usually take 2-5 minutes break every 2 hours or so. although (most of the time) I take a little bit more time than I allot to finish all the chapters, I reach the goal no matter what. After I finish what I had planned, I spend about an hour on eating, net surfing, watching TV, etc before I start studying again. turning cell phone or laptop off doesn't help at all if you don't turn your will off to spend time on those distractions.
Saying that, I better get back to studying - freaking organic chemistry test is just around the corner. 

good luck studying.