1. After you put the reed in water for a few minutes, place the reed in your mouth
with your lips on the thread and blow.
2. With a soft puff of air, it should produce a pianissimo note, C.
3. Increase the air pressure to produce a louder sound with the C and make it
produce an octave higher. The sound has to be produced gradually, that is, two
sounds at the same time in octaves.
4. If several "ugly" sounds are present, the reed is too open and out of control. The
reed has to sound clean.
5. If the reed sounds higher than C or C sharp, it will be impossible to play the oboe
in proper pitch. (You will play without control in dynamics and high in pitch, it is
something that you will not be able to avoid).
6. If the reed sounds lower than a C, it means that it is unstable, you will have to
use more embouchure and bite the reed to raise the pitch and, therefore, you will
probably play loud because you are biting, and without control (the instability of
the reed will not let you have control over dynamics, intonation and sound
7. So the main thing is that the reed sounds in two octaves to the sound of a C, and
that the opening of the reed is neither very closed nor very open.

8. An exercise to know if the reed has a good tuning is that while it produces sound,
take the reed out until it reaches no more than a minor third. This ensures that
the reed is flexible enough to control it. This is called pitch  floor.