Shamanism is a divine and interaction oriented school. They are heavily-reliant on their relationship to and strength of the spirits in an area. Generally Shamans are going to try and trade their way up the spiritual hierarchy. For example, one could start by building favor with the "Woma Python" spirit to get a meeting with the "Snake" spirit; then building favor with that "Snake" spirit to get a meeting with the "Reptile" spirit, and so on.
Spirits can be manipulated through the pre-negotiated use of symbols or gestures and a power source of some kind. Their uses can range from anything like picking locks, moving items, and driving people away to traveling to the Spirit World. But spirits can have their loyalty waver and depending on the number of practitioners they can be a finite resource within an area.
Because spirits come in different categories Shamanism could be seen as the root of many different arts, such as Chronomancy, which utilizes spirits of time, and Pyromancy, which uses spirits of fire.
↑Shamanism “Seven gods live in a grain of rice.” Spirits infuse everything, representing the material, immaterial and abstract forces that play into a given thing being what it is. Shamans communicate with these spirits and powers to invoke effects. -
Pact Dice: The Practices - Wbow Version
↑Shamans are interaction-heavy, quasi-religious in execution. They don't worship gods, however, but directly tap into and communicate with the 'little gods' or the spirits that drive things. At their most basic level, they can bid the spirit of a tree to emerge in a manifest form and have conversations with it, or ask it to do something.
Most shamans, especially those who settle in an area, are going to want to trade their way up the ladder. The hierarchy of spirits is such that, say, your pet snake Nibbles has a Nibbles spirit, (and Nibbles spirit is driven by lesser, incoherent hunger, heat, wellness spirits, but we won't go that small), and Nibbles spirit is influenced in a broader, general sense by a woma python spirit, which is influenced in turn by an even broader, general, (and greater) snake spirit, and the snake spirit is under the reptile spirit and the predator spirit, and those are under the fauna spirit and that's under the life spirit and so on.
So you set up or earn an audience with greater spirits and buy yourself influence. Powerful shamans who have an area they have custody over might well have a Fisher King effect, where the spirits they curry favor with or earn favor with can influence an area. You could pick anything you could name, really. If you pick snakes and encourage snakes then snakes are going to appear more in the area, they'll be taken more as pets, there'll be more snake tattoos. Sometimes this is abstract, and it's not always 100% easy to follow. Fertility might increase, risky childbirths might start to turn out more fortunate, people might come back from the brink of death more often, and mouse populations might start to drop as Snake wins its local war against Mouse... with consequences as the things Mouse has domain over start to be influenced.
A good scenario to point to is the existence of, say, the centipede spirit in Japan, which has been tied symbolically to industrialization and urbanization. It finds itself at odds with the mountain spirit, which has swept up the role of representing nature. There are shrines to each in a town, but as they're neglected and shamans fail in their duties, they each sweep up other ideas or have excess power that finds outlets, and weird shit happens. The mountain spirit starts producing ghosts and this becomes its unconscious expression of head-butting against the centipede, as more dead people become ghosts in the region, and the ghosts linger longer, and drive people out of the urban areas or make living in the city harder and scarier. Meanwhile, the centipede is doing much the same, but its outlet becomes the killer in the town, who ritually murders children (in the habit, not the practice sense, but...), who grows more powerful and monstrous. The small town with two dusty, overgrown shrines finds that a lot more people are seeing ghosts, dying mysteriously, or going missing while wandering at night. (Draoidhe/'Druids' are more the sub-/alternate subset of shamans who focus on these big, abstract, lesser-god style forces, but they'd start out more shaman-like and are essentially shamans of a different track.)
On the upside, however, cultivating a spirit and encouraging it can have positive effects. A Canadian Shaman might make bids and offer favors to a prosperity spirit, to encourage the finding of an oil deposit deep underground. Such a spirit might be fickle and unreliable, however, prone to making demands or taking as easily as it gives.
On the smaller level (and more favored by the itinerant and not-major shamans) is just knowing the things to say, having pre-arranged payments to spirits, or having spirits bottled or otherwise contained in vessels for use (limited or until the item breaks) for use of their influence over their domain. They can also transplant spirits or turn one into another (and have that execute IRL; say some words, break a charm, the smoke filling an area becomes fire), but this requires pretty specialized knowledge of a spirit type. I'll stress that its' an interaction-heavy school of practice, so most of the time you're going to need to have conversations or negotiate the price to get more complicated things to happen. With drawing of symbols and pre-arranged gestures it's pre-negotiated and the effects are generally smaller
Shamans are also one of the few practices who can just go and visit the spirit world; but this is hard and requires that some stuff be pre-established or else it's pretty harsh. In areas with shrines or other token nods to the spirit in question, it's a nice visit to what might be an especially cloudy or misty translation of the real world, where spirits appear like kids with masks and traditional clothes and where the greater spirits have a place to live. In areas without, it could be as bad as wading through a knee-deep tide of rodents, through maze-like corridors with steam and polluted exhaust spraying inconsistently through pipes, to reach the place where the mother rat is consorting with the human spirit, where prosperity is locked in mortal combat with destitution and the methamphetamine spirit is loudly and excitedly arguing how he should take the highest seat in the heart-chamber, and Community's answers are tired and hoarse from having fought so long, to so little effect. - Wildbow comment on Reddit