Choose a cue that is hard to miss
Good cues are events, not hopeful times. “After my first meeting” survives a late start better than “at 10:15”. The kettle clicking off, brushing your teeth, closing the laptop, and starting an ad break are all visible endings.
Make the attached action specific
“Move more” still leaves a decision. “After the kettle goes on, do calf raises until it boils” tells you when, where and what. Keep the first action small enough to do on a crowded day.
Use a minimum and an optional extra
Set the minimum at 30 seconds or one minute. If the gap is longer, continue. If it is not, the habit still happened. This prevents the expanded version from quietly becoming the only version that feels worthwhile.
Repeat before you optimise
Research on physical activity habits supports repeating behaviour in a consistent context, but people form habits at different rates. Keep one cue and movement stable long enough to learn whether they fit before adding a complicated rotation.