The first step to enhancing your concentration skills is to create the right environment. Make sure that you are comfortable but engaged. (Beware studying in bed! It usually leads to sleeping not studying.) Eliminate distractions by putting your phone away and using earplugs if you are in a loud environment.
Are you trying to study for hours on end without success? A better approach would be to give yourself small manageable blocks of study time and take frequent breaks. If you are struggling with a particularly difficult chapter or section, try setting a timer for 20 minutes. Take a 2-3-minute break after each 20-minute block. Your will waste less time re-reading and retain more if you study in short intervals rather than one long session.
Reading the textbook or course material is only the first step in studying. To retain information, try some active study techniques such as:
Eating well and getting enough sleep is critical to your academic success. Make sure you take mental breaks and make space for leisure time between study sessions. You are more likely to retain information when you are well rested and alert. If stress is affecting your concentration try some relaxation strategies such as exercise or meditation. If you find yourself worrying to excess, make an appointment with the counselling department.