Homework: See your teacher. Often, homework scores are low because a student has not answered all parts of a question or their answers lack the detail required for a higher score.
Quizzes/Tests: Spend additional time preparing. Remember you get only one try on every quiz, be prepared before you take the quiz. Make sure you are reading all the material that precedes quizzes and tests.
Consider completing Study Guides as a means of preparation. Often exam questions or very similar questions come from the study guides. Save the study guides and use them to review for the final exam. You can save the study guides in your Google Doc account just like you do for homework. The study guides are NOT graded, they are for your personal use.