I would begin studying by making flash cards for each of the main characters in the novel, particularly: Jack, Ralph, Piggy, Simon, Roger, Samneric, The Lord of the Flies.
On each flash card for the characters I would jot down one or two main quotes (especially for Ralph, Jack, Piggy, and Simon) and then some bullet points about that character's main contributions and actions in the novel.
Then, move onto the symbolism in Lord of the Flies. The major symbols are: the conch, fire, the beast, and the Lord of the Flies. For each of these symbols, make a new flash card and write a few bullet points down about the object's significance in the story,
It might also be helpful for you to take a sheet of blank paper and sketch out a general time line for the major events in the novel.
Lastly, make a new flashcard for each of the major themes of the novel--focus on the ones you remember your teacher discussing. Here are a few others: Civilization vs. Savagery, good vs. evil, friendship, hatred, violence, authority. If you know that the test will include short answer questions or essays, it would be worth your while to prepare some flashcards to study for the themes. Again, I would take the time to find some memorable quotes to go along with each theme to support your answer.
thanks lentzk, your answer was really helpful, again thanks a lot.