Assuming you are referring to a score on some sort of test or exam:
There are a few things you can do to improve your score. One is to make sure that you understand the material covered in the exam. This means going over your notes from class, doing practice problems, and/or reading any relevant textbook chapters.
Another thing you can do is to take practice exams under timed conditions. This will help you get used to working quickly and efficiently under pressure, which is often a significant part of exams. There are many websites that offer free practice exams (e.g., Exam SAM).
Finally, it is important to develop good test-taking strategies. This includes things like knowing when to guess on questions, how to eliminate answer choices on multiple choice questions, and how to pace yourself throughout the exam. Again, there are many resources available online that can provide tips and advice on these topics (e.g., Test Taking Tips).