The previous year question papers are usually available on the official website of the respective board of education for all the subjects. You can refer the official website or else, you may look up for certain reference books, question banks in which there are solved previous year question papers available. This will help you grasp the pattern of the question paper and know how to write the answers. Your teacher may also help you in explaining the pattern of question paper and giving sample papers. You may refer to your school library too for the papers. Hope this helps.