When using a household thermometer correctly, ensure that it is clean and dry, and check for any damage. For a mercury thermometer, you should grab the end without a metal end, vigorously shake it a few times, and swing the mercury back to the head of the thermometer, so that the mercury scale is below 35 ℃. For electronic thermometers, it is necessary to check if the battery is charged, as insufficient power can affect the measurement results.