By not spending the few minutes before an exam skimming over your notes or studying, you may not have a shot at being able to do well with cheating.   For essays, try to remember key words and points. Usually professors or teachers look for key words or important points; the essay's formal "fluff" is less important. If you know the topic or possible topics of an essay question, cram four to five terms or important points you know your professor will be looking for instead of studying everything, thereby reducing the effort required.  For math exams, try to memorise formulas. Knowing a formula can be more powerful that spending hours doing practice problems. If you can write down a formula enough to memorise it, then you can spend the test trying to apply those to the problems.  For multiple choice exams, try "chunking" information you know will be on the test. Instead of memorising a list of words, try breaking it into easier to remember smaller lists. For example, if studying for a history test, instead of remembering "Jefferson, Hamilton, Franklin, Washington, Grant, Lincoln, and Lee"  break it up into the "4 of the founding fathers: Franklin, Washington, Jefferson and Hamilton" and the "3 civil war leaders: Lee, Lincoln, Grant." By memorising the number of men to a specific topic, it'll be easier to narrow down who you are missing. Taking into consideration your current timetable, you can try to create your own study schedule.

TL;DR in Vietnamese:
Cố đừng học nhồi nhét quá nhiều vào giờ chót. Với bài thi tiếp theo, hãy bắt đầu học từ sớm và hiệu quả hơn.