I'm not sure exactly what type of question you need to answer, so I'll speak in general about answering questions about literature. There are a few things that most assessments will want you to demonstrate. You should be able to show in your answer:
- that you understand the expressed and implied meaning of the text. That means that you understood the story but were also able to construct meaning on your own. You could read deeply into the meaining of the story and draw conclusions that were not explicitly stated in the text.
- that you understand the entire story. You can relate different parts of the story together to come up with conclusions about the purpose or main idea of the story.
- that you can relate the story to your own life. You should be able to connect the story to something you have experienced or read about.
Another important factor is to make sure you answer the entire question. Sometimes a question has more than one part to it, and if you do not answer the whole question you will lose a lot of points on your answer.
Be sure to read the question carefully. Answer every part of the question, and when you are able, support your reasons and ideas with references and quotes from the work itself. Try and interest your reader by pulling him/her into your writing with an interesting story, quote, statistic, or rhetorical question--that's call the "hook". That will cover the content part.
If your weakness is spelling, grammar, and usage, there are many sites online that can and will help you improve your skills. Try a few of these:
It is always a good idea to include not only reference to the text and the context of meaning -- or what it means in its own time -- but what it means in today's context. Also, teachers love to read your opinions and perspectives on any topic because, guess what, we are students, too! Just make sure that your opinions are backed up by careful thought and do not contain sweeping statements that are open to misinterpretation.
In accord with #5, writing an argument is, indeed, effective. Also, the structure of the persuasive essay presents a strong, thoughtful thesis early and the support in an orderly fashion which provides the reader of your answer a clear, easily-read, response that has logical support to it. The clarity and logic of an answer are pluses, to be sure.
I'm not sure what grade you are at, but if you are confident in all of the help given above then a good way to show that you have extensive knowledge, is to pose an argument along with answering the question. It shows the examiner that you have been thinking for yourself and not just re-writting what you have been taught.