The Rebbe's guidance on studying Kabbalah:
An obligation and a privilege. Studying the inner dimension of the Torah, Chassidus and Kabbalah, is an obligation and a privilege, even before marriage — provided one learns from authentic sources (IK 7367). Its study and dissemination are tied to the coming of Moshiach (IK 510). Kabbalah should be studied and taught, heeding the Baal Shem Tov's warnings; even the Rambam was a great Kabbalist (IK 8332).
The right order. Study Kabbalah texts only after a solid grasp of the Chassidus one has learned, and then only the Kabbalah works that Chassidus cites (IK 9286).
Caution. Do not learn Kabbalah from controversial books, yet a book the Tzemach Tzedek cites must not be burned on the strength of rumors (IK 2469). Reject ideas contrary to Jewish faith and the Oral Torah, and beware of taking Kabbalah literally (IK 4660). Kabbalistic works should cite Chabad sources thoroughly (IK 8310).
See also: Kabbalah – The inner dimension of the Torah (Pnimiyus HaTorah); Torah study – Learning Chassidus; Kabbalah – Tzimtzum: literal or not.