One idea per card
The single most important rule: each card should test exactly one thing. SuperMemo's creator called this the "minimum information principle" — small, simple items are recalled cleanly and scheduled accurately.
A card that asks "Describe the causes of World War I" is really ten cards wearing a trenchcoat. You'll grade it inconsistently, forget half, and never know which half. Split it: one card per cause, each with a specific prompt.
Make the prompt do the work
A good prompt points at exactly one answer. "The capital of Australia?" is clean. "Australia?" is not — it could ask for the capital, the population, the continent, anything.
If a prompt could have several right answers, add a cue that narrows it: the category, the context, the first letter. Vague prompts train hesitation, not knowledge.
Use cloze deletions well
Cloze (fill-in-the-blank) cards are great for facts embedded in a sentence: "The powerhouse of the cell is the ___." They keep context while still forcing retrieval.
The trap is blanking out too much at once ("The ___ of the ___ is the ___") — now it's a guessing game. Delete one meaningful term per card and keep the rest as context.
Don't memorize lists verbatim
Ordered lists are the hardest thing to hold in memory and the most brittle. If you must learn one, don't make a single "list all 8 steps" card. Instead, use overlapping cloze cards (each hides one item) or a mnemonic, and add cards for what each item means.
The goal is understanding you can reconstruct, not a fragile recitation that collapses if you drop one item.
Make it meaningful
Cards that ask "why" and "how" beat pure "what" whenever the material has reasoning behind it. Understanding a fact makes it far easier to recall than memorizing it in isolation.
When a tool generates cards for you, this is where to spend your editing time: keep the atomic factual cards, and make sure the concepts you actually need to reason about are represented — not just definitions.