That's funny because I can't read tarot and you want to learn the pendulum that is really easy. XD
1 Find a small object and tie it to a small piece of cord, feel the weight and the way it slings to choose how long the cord has to be.
2 try simple questions with obvious yes/no answer like what's your name, what day is today
after a few question you should identify the way it slings if it's anwering yes or no.
Just try, but be carefull because as I said it depends on the user and be clear in your question or it will get confused, say it aloud if you feel doing so.
That's all I can tell you, it's matter of practice, and a little concentration.
Hope it helps =)