Getting a good study guide is probably the best method to prepare for the series 65 exam, but flash cards can make a great supplement.
Reading a study guide can get tiresome after a while, and you will likely need a break. Using flash cards is a great way to get away from your guidebook, while still studying.
It is well known that we memorize things the best through repetition, and flashcards are perfect for this. From elementary school to college and beyond, people make use of flashcards to learn. It is much more interactive and engaging than staring at a wall of text. The best material to learn on flash cards are vocabulary terms, mathematical formulas, and lists. Leave the complex ideas and theories for the study guides.
Make Your Own Cards
If you purchase a study guide and wish to save some money, you can make your own flashcards. Simple copy down information right from the guide, and onto index cards. This can be time consuming but if you are on a budget it might be worth it. You might be able to get a friend to help, especially if they are also taking the exam.
Another option is just buying flashcards premade. You can get a comprehensive set of flashcards for the Series 65 Exam here. Buying flashcards allows you get going, and start studying immediately. Plus, they will contain some material that you might have skipped.
Whether you choose you make your own or purchase some, flashcards are an awesome studying tool that you should make use of.