Pendulums should be cleansed before use for the first time and changed with your energy. By watching and observing the behaviour of your pendulum you can learn what responses it will give and how it personally acts towards you.
The easiest way to actually start working with a pendulum is to observe the pendulums responses when you ask it to show you yes and then show you no. do this a couple of times at least to start with so that you can be sure of the response. Over time it will become obvious to you which is yes and no but this can sometimes be less obvious when you are not used to working with them.
Another technique is using two pieces of paper one marked with yes, the other no and holding your pendulum over each piece of paper and watching which response it is drawn to when you ask it a specific question.
Pendulums are one of the few divination techniques that can be sued to give a yes/no answer.