Manage your time. Make a weekly schedule and devote a certain amount of time per day to studying. This will also improve your grades. That amount will vary depending on whether you're in high school or college, and also varies by field of study.
Study in 20-50 minute chunks. It takes time for your brain to form new long-term memories, and you can't just keep studying flat out. Take 5-10 minute breaks minimum and do something physically active to get your blood flowing and make you more alert. Do a few jumping jacks, run around your house, play with the dog, whatever it takes. Do just enough to get yourself pumped, but not worn out.
Find a good study spot. You should feel comfortable, but not so comfortable that you risk falling asleep--a bed isn't a very good study spot when you're tired! The place where you study should be relatively quiet (traffic outside your window and quiet library conversations are fine, but interrupting siblings and music blasting in the next room are not).
If you are easily distracted by social networking sites such as Youtube, Facebook, etc, then download application LetMeWork at http://img.labnol.org/files/18257/letmework.zip. Tried and tested, this will temporarily block these sites and help you study better. Double-click it to instantly block some of the distracting sites on your computer. When you are done with your work, double-click the same file again to unblock access to all the sites as before.
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