how can a person study effectively.
Studying, like any other skill, requires practice. What works for one person may not work for another, so you have to find your own technique. However, you can start with some ways others have found effective.
Study any particular topic for 15 minutes, then go to another. Go back to the first topic after a while to make sure you understand correctly what you think you've learned.
MAke an assignment calendar for every project/assignment you have for each class. Allow PLENTY of time for complicated assignments. Example: a 10-page report. Count the days until the due date (include only those days when you can study). Divide the time in half. The first half is for research. The second half can be divided into three parts: rough draft, final draft, and emergency time. Use the emergency time ONLY for times when some real emergency popped up and you couldn't meet the other deadlines.
When studying something that needs to be memorized, try flash cards. Carry several in you pocket at all times. Read one at every opportunity. It only takes a few seconds, but you will be surprised at how soon you will be able to replace those first cards with new ones.
Allow extra time to learn when you are tired, sick, or otherwise distracted. If you are dyslexic, WATCH YOUR HAND while writing. You will make fewer mistakes. This is especially helpful for math.
USe every possible way to stuff the knowledge into your computer-brain. Write. Read. Talk out loud. Draw. Finger write. Anything that helps. Music can help you learn a skill, but you need a piece that has rhythym and melody. Think of the song in the movie, Hans Christian Anderson, where the little inchworm song teaches simple math--2 and 2 are 4, 4 and 4 are 8, 8 and 8 are 16, 16 and 16 are 32.