How to write a flashcard that sticks

Hello there! If you are reading this, you probably have a deck full of cards that you hate reviewing. Maybe they are too long, maybe they are confusing, or maybe you just keep hitting "Again" on the same five cards every morning.

A little about me first. My name is Daniel. I am a third year engineering science student at the University of Toronto, specializing in machine intelligence. I also work on Nebulearn, so I have a conflict of interest here. I spend a lot of time thinking about how to make study sessions shorter.

The biggest mistake I see (and the one I made for years) is thinking that a flashcard should be a "summary" of a concept. It should not. A good flashcard is a single, sharp needle of information. If it is a paragraph, your brain will find a way to cheat, or worse, it will just give up.

The Minimum Information Principle

The most important rule for making flashcards is the Minimum Information Principle. It means that each card should contain only one discrete piece of information.

When you put three facts on one card, you create a bottleneck. If you remember two facts but forget the third, you have to fail the entire card. The scheduler then shows you the two facts you already knew way too often, just so you can keep practicing the one you forgot. This is how you end up with a massive review queue that feels like a chore.

If you break those three facts into three separate cards, you can clear the easy ones from your queue and focus your time only on the specific fact that is giving you trouble. You want your cards to be so small that the answer is almost instantaneous.

Using Cloze Deletions

A cloze deletion is just a "fill in the blank" card. Instead of a standard front and back question, you take a sentence and hide a specific part of it.

I find these much easier to write than standard questions because they preserve the context of the information. In my engineering courses, I often use them for definitions or properties of materials. For example, instead of asking "What is the primary characteristic of a brittle material?", I might write:

"Brittle materials exhibit [...] plastic deformation before failure." (Answer: very little / minimal)

This helps because the structure of the sentence acts as a hook for your memory. You are not just memorizing a definition in a vacuum; you are practicing how that fact fits into a statement. Most modern apps, including Anki and Nebulearn, support this format. If you are using Anki on an iPhone, you might have paid about $25 for the app, so make sure you are actually using the cloze feature to get your money's worth.

Why you must delete junk AI cards

AI has made it incredibly fast to generate cards from a PDF or a lecture note. I built a lot of those features into Nebulearn. But AI has a habit of being wordy. It loves to include "fluff" like "It is important to note that..." or it might create a card that is technically correct but incredibly boring to read.

You should treat AI generated cards as a draft, not a finished product. If you import a deck and find that the cards are too long, do not just push through them. Delete them. Or better yet, edit them down until they follow the minimum information principle.

A common trap is keeping a card because "it might be on the exam" even if the card is poorly written. If a card is bad, you will likely fail it during your session anyway. It is better to have 10 sharp, effective cards than 50 bloated ones that you end up skipping. You can read more about this in my post on flashcard mistakes students make.

Structuring your cards for speed

Speed is the unit that matters. The faster you can clear your queue, the more likely you are to actually do your reviews every day. This is why we focus so much on the best way to make flashcards rather than just making "more" cards.

Card Type	Best For	Effort to Write
Basic (Q&A)	Vocabulary, simple facts	Low
Cloze Deletion	Context, definitions, complex sentences	Medium
Image Occlusion	Diagrams, anatomy, maps	High

If you are studying for a final that is only a few days away, you might be tempted to use Quizlet because it is easy to find shared sets. That is fine for a quick cram session, but keep in mind that the free version of Quizlet uses session-scoped learning. It helps you master a set in one sitting, but it doesn't have a per-card due calendar like a real spaced repetition system. For long term retention, you need a scheduler like FSRS.

The one idea per card rule

If you take away nothing else, remember this: one idea per card. This is the foundation of how to use flashcards effectively.

When you are looking at a slide from your lecture, do not try to turn the whole slide into one card. Look for the "atomic" facts.

• Is there a name?
• Is there a date?
• Is there a specific relationship (X increases as Y decreases)?

Each of those is its own card. It feels like more work upfront because you end up with more cards, but your daily review time will actually go down because you won't be struggling with "heavy" cards that contain too much information.