Studying can be really hard, mostly when you have a lot of distractions around you, I like to change some things when I know I need to get some done, so lets start:
Set the mood, put the things that you know that you'll need close, if you go back and forward looking for supplies, you'll get distracted and loose time.
Don't get super comfy, I'm guilty of trying to find the comfiest spot in my house and that'll relax you and that's not going to help, find a place where you know you are going to work comfortable, preferably a clean surface.
Make a list of the things that you know you need to get done will help you to get it done and you'll be sure that you won't forget anything.
Take breaks, don't overload your brain with information, it won't be useful and you'll probably end up with a headache.I also think is important to really plan ahead, don't be a last minute person.
Finally, be aware that everyone has their own rhythms and ways to study and stay focused, this are the things that had been working for me through exams, maybe you have a better way, the important part is getting things done.