Gather the words you need. If you are studying for a standardized test such as the SATs or GREs, you can look in a test prep book or online to find lists of words you'll need to know. If you're studying a foreign language, you can find lists of words in any foreign language textbook.
Referring to your word list, write a word on one side of an index card. On the other side of the index card, write that word's definition.
Repeat this process until you have made as many cards as you like.