If you do consciously place your fingers on the planchette and it moves, a spirit may be using you as a catalyst to spell out the answers to your questions. A more popular belief is that your subconscious is answering the questions for you. Although it hasn't happened a lot, we have had occurrences where the planchette has moved without any of our fingers resting on it. When we sleep, our brainwaves change their patterns. It is thought that we are closer to the astral plane we when sleep, which is a plane in which spirits can easily communicate with us.
Angels are spirits, however they are inhuman spirits.
In other words these types of spirits have never walked the earth in human form. Demonic spirits are regarded to be fallen angels. In some instances, negative people will attract negative spirits. If a person is evil, there is a strong likelihood he will attract the attention of evil spirits. Dabbling in the occult can open the door to the demonic world.