Agree on the quiet period
Tell other occupants what you are checking. Consider scheduled appliances, irrigation, treatment equipment, and anything else that may use water automatically. Do not interrupt unfamiliar equipment or essential operations just to create a test. If use cannot be reliably paused, record that limitation instead of calling every change a leak.
The EPA home-maintenance page describes comparing readings during a period without water use. Gurnee's utility FAQ also discusses meter observations. Follow the relevant meter and utility instructions, and contact the utility when you cannot interpret the display.
Record numbers, times, and exceptions
Write the starting reading and time, then the ending reading and time. Keep the displayed units with the numbers. If someone uses water or an appliance runs, note it. A photo may help preserve a reading, provided it can be taken without entering a confined or wet space.
Do not remove seals, disconnect a device, enter a meter pit, or operate public controls. A missing or inaccessible meter is a reason to ask the utility for help, not to create your own access.
Treat the result as one clue
Movement with no accounted-for use deserves further questions. No movement during a short observation does not rule out intermittent leakage, drainage problems, or a source that is not metered there. Keep the result beside the water-bill comparison and visible symptoms. A provider can use those records to decide what to assess next without overstating what the meter proved.