• Each question should only have one answer.
• Questions should not contain redundancy.
• Questions should be simple. A more complex problem should be broken into smaller parts.
• Questions should be something you need.

Traps you can fall into with flashcards.

• Using off-the-shelf flashcard decks: You may think that pre-made flashcards save time, but many of the pre-made decks need editing to fit your purpose.
• Bad card design: Simply copy and paste stuff from classes can be fast but make memorising a mess.
• Memorisation instead of understanding. Memorisation should follow understanding, not replace it.
• Flashcards are a fake substitute for doing real learning. Doing lots of flashcards may leave the impression that you have learned a lot, but it is not true for complex subjects.

Flashcards are vastly superior to passive review techniques. They work well when used appropriately.

If you have used flashcards before, but they were not effective, chances are you either designed the cards badly or other forms of practice may work better for you. If you love flashcards, go forward with caution. Ask if flashcards are really enhancing your learning.