I would wave to agree with the last reply as well. You can influence outcomes. It is almost a discipline to keep your own thoughts and wishes out of answers received in tools such as tarot, pendulums, runes, ect.
In general, clearing the mind is key in both meditation and receiving answers not of your own initiation.
It is also possible what you are looking for in seance and pendulums is an indirect path through wich you may find your own abilities and gifts communicating w/spirit.