Witch bottles work for one to five years. Image light streaming from the bristles, and aim it around the room, invoking hallowing power. Placing a broom upside-down against the door is an old spell to bar negativity from entering. Malignant force thrives in filth and grime. Cleanliness thwarts negativity.
Poltergeists are often the effect of a female teenager who is enduring stress.
They are rarely caused by spirits. Many second-hand items retain the imprint of their original owners, and may be sources of psychic trouble. Some religious items may be antipathetic to you. Some individuals are harmonious with one set of religious items, but ill-disposed to others. This only denotes that the person is somehow at odds with those aspects of religion symbolized by those items.