If you managed to get good grades at midterms, you would be eager to maintain this achievement until the end of the semester, and next semester. However, if your grades already bad, then you have to try harder than ever.
Consider the following tips:
Read each week
Some teachers require that you read a book every week, several other professors might just make it as a reference. Sometimes, reading assignment is listed in the course syllabus and it can make us overwhelmed each week. However, force yourself to read and meet targets in the plan of studies.
You will discover how your ability to understand the lecture material increases with diligence reading the book according to the assignment.