Shamanism, much like druidism, is based largely on the spirit of the natural world. It is a tradition of respect for the spirits of all things, rather than worship or control. All things possess a spirit, though the spirits of living creatures are easier to contact and understand than those of inanimate objects, or even plants. Nevertheless, everything in existence possesses a spirit in one form or another, though it is sometimes almost impossible to detect.
It is very difficult to generalize on the nature of shamanism, as many cultures in history, from the Native American and Central/South American tribes, to the Celts and even African tribes, had their own beliefs and viewpoints regarding the practice and communion with the spirits. As such I will continue this treatise based on what I was taught by my mentor, from the perspective of a Central American tribe, though I will include what basic knowledge I know of the workings of other civilizations of shamanic belief.
The primary spirit that a shaman will come into contact with is that of his own totem(s). Depending on the specific tradition of shamanism, a person can have one or many totems. My own tradition, which is descendant from that of the ancient Tolteca of Mexico and Central America, says that each person has four totems: one for each of the body, mind, and soul, plus one additional, secret totem, that is known only to oneself and his teacher. This fourth totem is a gift of sorts from one's teacher, who requests that one of their totems attach themselves to the student, so that in one sense, the teacher is always with their student. Most variations of shamanism, though, only speak of one totem spirit.
Most totems take the form of a natural creature, though some are more esoteric. This is, in large part, because when the tradition was at its height, the belief in these totem creatures elevated the power and strength of these beings, raising them from simple animal spirits to the status of Totem Spirits.
A shaman does not pick his totem. Rather, the totem chooses the shaman. Throughout their lives prior to taking the role of a shaman, an initiate is usually drawn to a specific creature, without realizing the implications of this. From a very young age, the initiate will have thought of this creature, either through something as simple as wanting one for a pet or collecting information and the like on these creatures. I myself was always drawn to the mythical firebird of legend, and would spend hours doodling such creatures on every piece of paper in front of me, daydreaming of being able to turn into one, and dreaming about them at night. It was not until much later that I learned of my connection to Firebird.
Normally, an initiate shaman will be introduced to his totem through a visionquest. These can take various forms, from sweatlodges and ceremonial pipesmoking to deep meditation and "Out of Body Experiences." My own visionquest took the form of a spirit walk, which my mentor walked me through. I left my physical body and traveled to a place where I felt safe. In this place, which for me took the form of a serene mountaintop overlooking a verdant valley, my Totem, Firebird, sat waiting for me. For what seemed an eternity, he just stared into my eyes, though it felt more like he was staring through me. After some time, he simply nodded once. My mentor, who had accompanied me the entire trip, introduced me to him, and him to me, at which point Firebird let out a cry and took flight. I returned to my body, suddenly aware of a suge of energy flowing through me. Everything seemed much crisper, and more vibrant. I had been accepted.
I later learned that the vibrancy of the world around me at that moment was due to shapeshifting. This is another aspect of the arts that a shaman is naturally attuned to. Rather than a physical changing of form, however, shapeshifting is a primarily mental exercise. In essence, it involves shifting your perceptions to those of another creature in order to enjoy a different viewpoint on the subject at hand. Usually this involves studying the creature/animal for a while to understand its strengths, then forcing yourself to assume those strengths that you normally do not possess. This will help get a fresh perspective of a problem facing you, and is one of the key aspects of shamanism.
So, you ask, what about spells? What can a shaman do with his abilities? Well, that entirely depends on the path the shaman walks, and on his totem(s). Remember, a shaman's ability and power are derived in part from his connection to the spirits. Their totem chooses them because they mesh well with the totem's own "personality." That is, a shaman will not generally be able to cause an effect that is in direct opposition to the nature of the totem. As an example, Firebird, who represents eternal passion and emotion, would not assist me in a spell that would dull my own or another's emotions, since it is anathema to its basic nature. I could still try to cast the spell, but without my totem's assistance, the spell would be much more difficult to cast, and therefore have a lower chance of success.
One thing that a shaman must keep in mind when casting a spell is that he needs to ASK for assistance from the spirits. Remember, a shaman's relations with the spirits directly affects his abilities, and one thing all spirits have in common is their desire for respect. NEVER EVER demand anything of a spirit. Always ask for assistance, and trust that if they deny your request, they have good reason to do so. Also remember that sometimes they may turn around and ask you to do something for them in exchange. Never renege on a promise to assist them, for they will turn their back on you and you'll be lost. In my experience, the spirits know your capabilities at least as well as you do, and will never ask for anything they do not believe you can accomplish. They don't always tell you right away what, if any, favor they will ask of you in exchange for their assistance. Sometimes you just have to wait and see.
How do you know what they want you to do in exchange? That all depends. Sometimes, they will come to you in a dream or vision, or sometimes you will just know what it is they want. And again, sometimes they won't want anything. That, however, depends on how you treat them. The friendlier you are with them, the less they will ask of you. You will know how important something is to them if you are really respectful, polite, and supplicant when you ask their assistance, and they still ask something of you.
What kinds of things will they ask of you? Again, that depends on the spirit and the situation. Sometimes it is a simple task that you would have done anyway, and sometimes it is a little more involved. Such things include a promise to act in a certain manner in certain situations, or do something at a specific time or place. It is difficult to get into here, because so much of it depends on your relationship with the spirit in question, and what you have asked of it.
So much of shamanism is based on the personal level that it is difficult to provide truly general information. As well, since there are so many variations based on culture, no text can really provide a "This is how this is done" example. What I'm trying to say here is that if you find your totem, and the path that suits you best, then follow it. There are many techniques for finding your totem and your path, as I have already stated. The only thing I can truly say is try, and see what happens.
A word of caution, though: The path of the Shaman is not exactly an easy one. It involves a lot of discipline, and can be very demanding. The spirits are really beyond our comprehension, and who really knows why they do the things they do? I have practised the art for 6 years, and I still have no idea.
Some other things that are important to the art of shamanism include geomancy (the art of discerning and manipulating the natural flows of energy in the world), astral projection, shapeshifting (described above), and the arts of diplomacy and negotiation. These tools help to understand the spirits, and yourself, better, thereby making the path of the shaman a bit easier to travel along.
