Use expanding review intervals

Review soon after first learning, then at progressively longer gaps as memory strengthens.

Why it works

A memory you can just barely retrieve gains the most from being retrieved. Expanding the gap keeps each review near that edge of difficulty: early reviews catch the fast initial forgetting, and later, wider gaps match the slower decay of a now-stronger trace.

How to do it

1. Schedule the first review within a day of learning, while the trace is still fragile.
2. Lengthen each subsequent interval (days, then weeks, then months) as recall succeeds.
3. Shorten the interval again whenever a review fails — let difficulty steer the schedule.

Evidence

Expanding-interval schedules reliably outperform massed review for long-term retention. Whether expanding beats a fixed equal spacing is more mixed, but both beat cramming. (rct)

The exact expanding schedule matters less than that gaps exist and grow roughly with mastery; do not over-tune the numbers.

Common mistake

Reviewing on a flat, frequent schedule forever, which wastes effort on items already well known and starves the ones near forgetting.