Generally, high magic is understood to have a very strong ceremonial aspect to it and a focus upon abstract concepts. Low magic, on the other hand, is understood to have a more improvised element and focuses on more concrete ideas and immediate concerns. There are schools of magic that lend themselves towards highly ceremonial magical study. Frequently, high magic that is focused upon ceremonial elements is the heritage of ritual magicians of earlier eras. Low magic tends to manifest most frequently as folk magic.
The schools of achemy, theurgy, and ceremonial necromancy could be classed as high magic. Many modern spirit manipulative magic, chaos magic, and technologically based magic fall under the category of modern folk magic. Each school of magic has their own specialized set of tools and practices. Each has their own traditional focus of inquiry. While there are components from each school that can be applied to other schools, the primary practices are what is considered when determining if something is part of a given school of magic.
Alchemy is perhaps one of the oldest forms of magical study. The language of alchemy is specialized and can be difficult to make sense of with out an understanding of what the symbolism used means. This specialized language makes the texts that we have access to difficult to comprehend but it is also a mark of high magic. Many of the tools of alchemy, such as the alembic, have persisted into modern day, non occult use, morphing into the recognizable laboratory equipment.
Theurgy, which is argued to be a forerunner of alchemy, is the ritual invocation of deity and spiritual beings for magical purpose. It is from here that ceremonial magicians acquired the use of ritual circles and sigils. Additionally, the practice of invocations of a formulaic nature are derived from this school of magic. When one considers the works of John Dee and his recording of Enochian magic, it is possible to see how his work is heavily influenced by earlier techniques that are alluded to in the Malleus Maleficarum and related works from the Burning Times.
Both alchemy and theurgy have fairly standardized ritual practices within Western culture. They have their respective foci upon the refinement of the soul and the union of the soul with the divine. Each system of magical study has their own specialized language and symbolism. They are also shown to have their own set of tools.
Chaos magic has no standardized ritual format. It incorporates elements that a given practitioner feels would prove useful to them. It is very individualistic and experientially based. The focus of study ranges wildly, though trends suggest that a study in the manipulation of time is currently popular. There is a lack of unique tools, terms, or symbolism. The individual practitioner (sometimes known as a chaote) uses whatever means proves expedient. As such, there is no set of required elements or correspondences used.
Technological magic has grown up alongside chaos magic. With the advent of computers, there are many modern occultists who employ this tool extensively. Their work has very few unifying qualities. The focus of inquiry is as varied as the practitioners themselves. Technological magic uses available technology as the vehicle by which occult elements are engaged and manipulated. A fine example of this is the use of Google as a divination tool. The search engine can be used in a randomized fashion much like a bible is for bibliomancy. The first result is generally the answer to the query.
There are countless different ways to divide the study of magic and the philosophical lines of inquiry engaged by occultists and magicians. Categorizing them by their common elements, it is possible to define general schools of magical study and philosophy. Unfortunately, there is no standardized discussion of magical schools of thought. As such, the organization of one's research into respective schools will be different for each person engaged in study.