A fine piece. However, in my not remotely humble opinion, the most important lesson in that introduction is this: Don't try to consciously preach or inflict a message on your readers. Instead, simply focus on telling a great story, and what is important to you will be inherent therein in any case.

From Tolkien's Foreword:

"As for any inner meaning or 'message', it has in the intention of the author none. It is neither allegorical nor topical."

Later, he writes:

"I cordially dislike allegory in all its manifestations, and always have done so since I grew old and wary enough to detect its presence. I much prefer history, true or feigned, with its varied applicability to the thought and experience of readers. I think that many confuse 'applicability' with 'allegory'; but the one resides in the freedom of the reader, and the other in the purposed domination of the author. An author cannot of course remain wholly unaffected by his experience, but the ways in which a story-germ uses the soil of experience are extremely complex, and attempts to define the process are at best guesses from evidence that is inadequate and ambiguous."

From The Lord of the Rings, much can be extrapolated about what is important to Tolkien, but none of it comes off as preachy, precisely because he didn't consciously set out to deliver a heavy-handed message. I wish more authors would learn from his example, rather than grinding self-conscious, sanctimonious, condescending axes that come off as finger-wagging. I've written about this subject in more detail here, if you're interested. :)