From around week 28, your OB will ask you to track fetal movement. Sit somewhere comfortable, count until you reach 10. Most people get there in under 30 minutes.
Counting kicks is most useful as a baseline you check against — every baby has their own pattern. If you notice a clear, sustained decrease in movement compared to your normal, call your provider right away. Don't wait. Kick counts aren't a diagnostic tool, but they're how thousands of stillbirths are caught early every year.