Read each of the Harry Potter books, even if you have read them before. While reading, take notes about the events of the book and write down any words or names you do not understand so that you can look them up later. In addition to the seven books in the Harry Potter series, read the spin-off books "Quiddich Through the Ages," "Fantastic Beasts and Where to Find Them" and "The Tales of Beedle the Bard" for additional information about the Harry Potter universe.
Watch each of the Harry Potter movies. Although there are differences between the book to the movie, the movies can provide you with visual clues and clarifications. Refer to your notes while watching the movies to see which events from the books were left out or altered.
Read official Harry Potter web pages, such as author J.K. Rowling's homepage, for additional information, theory and analysis not found in the books.
Test yourself on your Harry Potter knowledge by completing online quizzes at the official Harry Potter web pages. Play Harry Potter trivia board games such as "Scene It? Harry Potter Edition" to further test your knowledge. Write down the answers you miss for further study.
Join a book club, attend a Harry Potter fan convention or participate in Harry Potter discussions on online message boards to further improve your Harry Potter knowledge.