Spirit possession and hakata (dice sets, shells, bones, seeds) are two of the divination methods they use.
"The impact of traditional medicine in Zimbabwe is intricately linked to the operations of traditional healer as the chief practitioner. The traditional healer performs multiple functions as diviner by diagnosing the causes of sickness, misfortune and death; as herbalist he dispenses medicines and as healer he promotes health and wellbeing of the Shona through rituals and treatments. The Shona use a common term "n'anga" to describe his roles as traditional medical practitioner. Traditional medicine is used for various purposes that include preservation of morality, good luck charms, contraception, psychological and spiritual problems. In fact the traditional medical practitioner has multiple functions, in addition to being a medical practitioner, the traditional healer is a religious consultant, a legal and political adviser, a marriage counselor, a police detective and a social worker." - Tabona Shoko
"The n’anga’s primary function is healing. As a traditional medical practitioner he provides both physical and spiritual healing. Healing involves both the individual and society. He also acts as an intermediary between the human and spiritual world. He is consulted on medical, economic, political and social issues." - Tabona Shoko
"Another important aspect of Shona culture are the n'anga, medicine men (and women) or "witchdoctors." Their healing methods include spiritual guidance as well as traditional herbal medicine (muti), since in the traditional Shona worldview many physical ailments have spiritual causes. A n'anga may consult the ancestral spirits to determine whether a taboo has been violated or a ritual omitted, and then advise his or her patient on how to appease the spirits." - Marin Theatre Company
"The njuzu [water spirit] is an important part of Shona mythology. They are supposed to live in deep lakes and rivers, and may lure the unwary person into the water. Those who return from this experience are more likely to become a n'anga [witchdoctor], as they have travelled between the physical and spiritual worlds." - Guruve
"Njuzu can be extremely kind and generous. She is a wise spirit, a repository of knowledge. If captives pass her tests, they essentially become her apprentices to whom she bestows information and teaches various healing arts. Eventually, if all goes well, a kidnapped person is sent back home with a basket filled with magical medicines (mushonga). Njuzu has supplied this person with the skills, knowledge, and tools needed to become a potent and successful healer. The process can take a year or longer." - Occult World
"While they are away, the person is trained in the spirit world by the njuzu and when they return to the physical world they are very likely to become a n'anga or traditional healer - because they have already been to the spirit world and they know how to travel between the two dimensions."
The njuzu is half human, half fish and is always female, so it is no surprise that it is often represented in Shona sculpture very much like our mermaids." - Guruve
"A n’anga divines by mechanical means using items like hakata (dice) or a talking calabash. Nowadays objects like a mirror, water, cloth or paper are used to identify the causes of the problem. Diagnosis can also be effected through omens, dreams and ordeals. The spirit world reveals and communicates to the practitioner through various forms of phenomena. According to one n’anga nature speaks to you through trees, grass and animals as invisible spiritual forces. A n’anga uses a third eye to look inside. He identifies the cause and attacks pain in three ways: physical, psychological and spiritual. Elders in the Karanga society are also equipped with basic knowledge of diagnosis through dreams, omens and observations. The n’anga divines. He is more powerful then the elders." - Tabona Shoko