Common beliefs are shared by all forms of shamanism:
Shamanism is based on the premise that the visible world is pervaded by invisible forces or spirits which affect the lives of the living. Although the causes of disease lie in the spiritual realm, inspired by malicious spirits, both spiritual and physical methods are used to heal. Commonly, a shaman “enters the body” of the patient to confront the spiritual infirmity and heals by banishing the infectious spirit.
Many shamans have expert knowledge of medicinal plants native to their area, and an herbal treatment is often prescribed. In many places shamans learn directly from the plants, harnessing their effects and healing properties, after obtaining permission from the indwelling or patron spirits. In the Peruvian Amazon Basin, shamans and curanderos use medicine songs called icaros to evoke spirits. Before a spirit can be summoned it must teach the shaman its song. The use of totemic items such as rocks with special powers and an animating spirit is common.
Soul - This concept can generally explain more, seemingly unassociated phenomena in shamanism
Healing - This concept may be based closely on the soul concepts of the belief system of the people served by the shaman. It may consist of the supposed retrieving the lost soul of the ill person. See also the soul dualism concept.
Scarcity of hunted game - This problem can be solved by “releasing” the souls of the animals from their hidden abodes. Besides that, many taboos may prescribe the behavior of people towards game, so that the souls of the animals do not feel angry or hurt, or the pleased soul of the already killed prey can tell the other, still living animals, that they can allow themselves to be caught and killed.
Infertility of women - This problem is thought to be cured by obtaining the soul of the expected child
Spirits - The Heteri believe in spirits - those of the otherworld, nature, and the dead. Most spirits are invisible and can not be seen without the involvement of a Magician (Shaman) or Priest, though many common folk have dreams or get messages from their ancestors. Spirits can possess people and animals, bring curses or bad omens. All of these call for the work and defense of the shaman.
Priests reveal the truth of the gods and bring their will to the physical world and bring order to it.
Shamans seek understanding and stewardship of both the natural and otherworldly forces.
Italicized sections are quotes from Wikipedia:Shamanism until I get correct wordings substituted.