Using a Liquid-in-Glass Thermometer

Treat the instrument with care - the glass bulb is easily broken.
Immerse the bulb in the substance and wait until the thread in the tube settles to a steady value - it takes time for a liquid to expand or contract.
It is best to keep the bulb immersed all of the time otherwise the thermometer will start to adjust to room temperature - if you have to leave it standing in the container be careful to check the stability of the apparatus before you let go of it - otherwise make sure that it has time to adjust before you take the next reading!
Take care - while holding a thermometer as you heat a container of liquid you have to make sure you do not burn yourself or set fire to the sleeve of your labcoat.
Stir gently for about ten seconds before you intend to take the reading - some parts may be hotter or cooler than others
Take the reading at eye level (care if heating not to set your hair alight!)
Double check that you understand what each division on the scale represents and get a friend to check the reading.