Be as systematic as possible in setting your goals. One way to be systematic is to use a table to make a list of items you want to consider. See a tutor. Do all the homework problems. Form a study group.
Review notes right after class.
Study in one-hour sessions with breaks. Make practice exams. Cut back on the number of hours of work per week. Keep a daily diary for one month to see if I can identify wasted time. One good aspect of brainstorming is that items on one list can be used to brainstorm another list.