The true "practice" of Kabbalah involves techniques aimed specifically at altering natural states or events--techniques such as the ritual incantation of Divine Names or the inscription of such names (or those of the angels) upon specially prepared amulets. Though often termed an "occult" tradition, Kabbalah ma'asit is meant to be employed by only the most saintly and responsible of individuals and for no other purpose than the benefit of man or Creation.
As far back as the time of the holy Ari (the mid 16th century), there are indications of these techniques being abused by unfit practitioners. The holy Ari himself exhorted his disciples to avoid the practical arts of Kabbalah, as he deemed such practice unwarranted so long as the state of ritual purity necessary for service in the Holy Temple remains unattainable. The Ari's exhortation in effect deferred the practice of ritual Kabbalah to such time as when the Temple will be rebuilt and the requisite purity which its service requires be restored.
The Temple service indeed provided the primary framework within which the practical aspect of Kabbalah evolved. The cardinal rite of the practical tradition--enunciating God's essential Name--was a centerpiece of the Temple rite conducted by the High Priest on Yom Kippur. Like other aspects of the practical tradition, the exact formula for pronouncing the four-letter Name was passed on in secrecy from generation to generation of High Priest. At some point it was determined that this formula should no longer be transmitted, as the individuals appointed to the High Priesthood proved increasingly corrupt and unworthy of executing this sensitive and spiritually demanding practice. By suspending the ceremonial incantation of God's Name in the Temple, the Rabbis provided a precedent for those, like the Ari, who in later generations argued against the practice of ritual Kabbalah.
Indeed, the Ari's fears proved to be well-founded as in the ensuing centuries we have witnessed the emergence of pseudo-Kabbalistic movements, driven by either rank opportunism or misguided spirituality, which have compromised the faith of Israel as well as the reputation of legitimate Kabbalistic pursuit. The study of Kabbalah's conceptual foundations within a context of unwavering commitment to normative Torah law provides the best hedge against these corrupt forms of Kabbalistic practice.
As indicated above, there is no clear demarcation separating the contemplative elements of Kabbalah from those aimed at influencing or altering reality. Just as Kabbalah iyunit can influence, through its system of kavanot (guided meditations), the configuration of Divine forces impinging upon our reality, so too is the efficacy of "practical Kabbalah" predicated upon the knowledge of Kabbalistic theory and doctrine. Perhaps the most renowned case of Kabbalistic practice-the fashioning of a golem (humanoid) in 16th century Prague-involved none other than the great scholar and saint, Rabbi Judah Loew, a leading interpreter of the contemplative tradition.