Pendulums can be fun. But they do require a lot of filtering. In my own experience, they have been more effective as a link to the subconscious than a divination tool like tarot.
The way a question is asked is very important, and the person's own desire of the situation can be revealed more than the actual answer.
For example, asking a "will this happen?" question is not really a good idea, since it's not really predictable. Asking "is (this option) optional for me?" is much better.
But if you really want (this option) to be the best answer, your own desire can give you a yes answer.
It's partly why having carefully worded questions, and being in the right state of mind (and you have to determine exactly what that means for you) are very important.
Some people may literally dowse with a pendulum, but I have not tried.
Another thing to consider is more than just yes-no questions. You can make a dowsing board, and use the pendulum to indicate answers according to how the board is laid out.
Some basic practice to get used to a pendulum: Hold it at different lengths, and ask "What is yes?" and "What is no?" and "What is waiting for a question?" "What is no answer?" Your results may well be different from mine. Just know your answers.
And study! Read a bit about pendulum use. There's a surprising amount out there, sometimes mixed in with some far-fetched information in my opinion, but it's out there nonetheless.