I use the index cards with my students each year. Students can either print their own copy (or we print them for a minimal fee). Part of the weekly homework involves self-testing with the cards.
If your printer has duplex printing options, choose "flip on short edge" to get the question and answer to line up properly. Print them on the thickest card you can afford so that the answers cannot be seen through the card.
Students use the index cards as part of their weekly indepedent study tasks. Early in the course, I will set specific cards to practise, but as the course progresses and more index cards are given out the task becomes more flexible and students often choose their own cards to work on.
Once a week/fortnight we do a mini-test in lesson.