Have ready all the things you need, such as pens or calculator. Study at a time when you are alert and not hungry or sleepy. Don't wait until the last minute to study. Short, daily study sessions are better than one long session the night before the test. Set a goal for each study period.
Repetition is key.
Read and reread your class notes and the relevant chapters in the textbook. While you are reviewing your notes, cover them up periodically and summarize them out loud. Pretend you are explaining the material to someone else. Do any practice exams or study sheets provided by the teacher. These will help focus your study session and give you confidence.