Great article on How to Create Great Teachers. It's focused on K-12 education primarily, but there is wisdom in the discussion relevant to workplace learning.

Here's the major points I take away:

  1. Great teachers need deep content knowledge.
  2. Great teachers need good classroom-management verbalization skills.
  3. Great teachers need their content knowledge to be fluently available to them in the context of typical classroom situations. To get this fluency, they need to practice in such situations—and practice linking actions (especially their verbal utterances) to specific classroom situations.