Calibrating a pendulum is relatively easy. Simply hold your pendulum in your receptive (usually left) hand and keep your elbow braced so there is no strain in keeping the pendulum suspended. Next, concentrate on the pendulum and ask it (effectively you are asking your subconscious) out loud to show you its "yes". Next ask it to show you its "no".
These are the most basic results that you will need. If you wish you can also try calibrating the pendulum with "maybe" or "I don't know" etc. Or anything else that you think you may find useful.
Each time you ask the pendulum to show you its movement, watch carefully to see which direction (or how) it moves. This may be movement to the left, the right, away from you, towards you, circular in either direction etc. The movements may be very, very, slight to start with, but as you become more in tune with the pendulum and your higher self the movements will become stronger and more definite. Don't try and force the movements because they seem small.
Once you have calibrated your pendulum try it out with simple questions to which you know the answer.
It is a good idea to calibrate the pendulum before each session. Although you will probably find that nothing has changed it pays to make sure. The last thing you want to do is to wrongly interpret an answer when the issue at hand is important.