“It is the apprentice’s duty to learn all that he can from the Master, and the Master’s right to refrain from revealing all of his secrets.”~Darth Sidious
I don’t entirely agree with many of the things this character said on the subject, but I rather like the sentiment here. Though I would add that its also the Masters responsibility to enable his apprentice. Not to do things for him, but to subtley generate oppurunities for the apprentice to do things on his or her own. For the purpose of guiding the apprentice in the artform of seizing them, yes. But also to generate oppurtunities that, if taken, will lead to a somewhat known outcome.
Cunning, subtlety, and mindfullness are integral; on the part of a Sith practitioner in general as well as in the relationship of an apprenticeship. The guide must be perceptive to affect his student towards transforming as an individual and must shroud certain elements of the path in darkness, so that the student can make his own discoveries and, in essence, become a being of the Dark Side in his own right. The student must be ambitious enough to grow and evolve into what I call Sith.
“There were numerous other branches of Sith knowledge that were not taught in the academies or by… masters…. the apprentice was expected to research such things himself. Darth Zannah learned… sorcery from several ancient manuscripts… mastering many unique and frightening abilities.”~Sith Training, (Paraphrasing) Wookiepedia