Mercury column has a kink in it- one has to shake the column down to say 97 degrees F to be able to use to get a new reading.
Some shake down with arm movements and wrist snaps.
Wrap the thermometer in paper towel, put in a long sock, and whip the sock around in a circle. Do this in wide open spaces.
Under tongue, at least 2min. 3 may be best.
98.6 is the norm for oral. Diff people and diff time of day diff reading.
Armpit and also anal norms are diff. Kids prob diff to.