Create a routine that works for you and stick with it. You might have to experiment until you find it.
Make sure you ate a healthy filling meal before you study so you have plenty of energy. But don't overeat because if that happens you might feel sleepy and won't be able to focus.
Make sure you stay hydrated. Drinking water helps the brain function, avoids headaches and boosts your concentration and memory.
Break up your study time in manageable chunks of time. Take a break and come back to your study materials, even if that means studying for 15 minutes at a time and taking 10 minute breaks in between. Using a timer can help with managing your time.
Remove any distractions from your study place, mute your cell phone or leave it in another room all together. Find a spot where nobody will interrupt you. If you like listening to music while studying, choose calm instrumental music.
Identify which learning style you are more comfortable with and find resources that cater to your preferred learning style. You might prefer to study by yourself, with a peer or in a study group. You might prefer to learn by reading and writing or by watching a video and drawing a scheme with the main concepts of the lesson.
Don't leave studying for the last moment. Use a calendar, to-do list or schedule to help you plan your study time and plan ahaed.
Make sure you set realistic goals. For example, if you have 3 hours to study every day, allow 60% of that time for study while allowing some flexibility and room for breaks or other needs.
Make it easy on yourself. If you plan on studying early in the morning, set your goals and your study space with everything you will need the night before. If you study in the evening, set up your study space early in the day before you head out of your home, this way, when you come back, your study materials will be ready for you. Realize that you can't rely solely on motivation to accomplish your goals. Motivation fluctuates so something that seemed easy when you were motivated might feel really difficult when you are not. Always do just a little bit less than you can. Do not overdo it because your brain will remember the extra effort you put in when you were motivated and, when you are not so motivated, it will feel much more difficult to get started.
If you have trouble getting big projects started, break them into small achievable tasks. For example, if you have to write a research paper, on day 1 research reliable sites where you can find the information you need, skim through them and write down the name of the few sites that you will use for your paper. On day 2 read the first site thoroughly and jot down notes. day 3 read the second site thoroughly and jot down notes. On day 4 read the third site thoroughly and jot down notes (and so on). The following day, check all your notes and determine if you have enough information. The following day write a summary of your notes. And continue the process by doing only one task a day.