Write better cards
Keep each card to one idea. A card that asks for a single fact is easy to grade honestly and quick to review; a card that crams in five things is hard to recall and easy to fool yourself on.
Ask for recall, not recognition. 'What is the capital of France?' is better than 'Is Paris the capital of France?' Phrase the prompt so you have to produce the answer, not just confirm it. Add a cue or image when it helps the answer stick.
Study them the right way
Always answer before you flip — even a guess. The moment of retrieval is where the learning happens. Be honest about whether you got it right; the system only helps if your grading is truthful.
Review on a spaced schedule rather than drilling the same deck over and over in one sitting. Mix decks or subjects to interleave. If you're using software like Koydo, this is handled for you — you just do the cards that come up each day.
Avoid the common traps
Don't make giant cards, don't review only the cards you already know (they feel good but teach little), and don't cram the night before. A few minutes most days beats a marathon once a week.
If writing good cards is the part you dread, a curated library helps — Koydo's curated decks are written and attributed for you, so you can study instead of building decks.

