Can you describe some principles of good Linux advocacy ?

There are several papers of different quality devoted to this issue. Generally one should avoid practice of used car salesmen like a plague. Linux Advocacy Guidelines looks pretty reasonable for me. It contains a extremely useful canon of conduct: "Avoid hyperbole and unsubstantiated claims at all costs. It's unprofessional and will result in unproductive discussions." IMHO canons still extremely current and it make sense to reproduce all of them:

• As a representative of the Linux community, participate in mailing list and newsgroup discussions in a professional manner. Refrain from name-calling and use of vulgar language. Consider yourself a member of a virtual corporation with Mr. Torvalds as your CEO. Your words will either enhance or degrade the image the reader has of the Linux community.
• Avoid hyperbole and unsubstantiated claims at all costs. It's unprofessional and will result in unproductive discussions.
• A thoughtful, well-reasoned response to a posting will not only provide insight for your readers, but will also increase their respect for your knowledge and abilities.
• Don't bite if offered flame-bait. Too many threads degenerate into a ``My O/S is better than your O/S'' argument. Let's accurately describe the capabilities of Linux and leave it at that.
• Always remember that if you insult or are disrespectful to someone, their negative experience may be shared with many others. If you do offend someone, please try to make amends.
• Focus on what Linux has to offer. There is no need to bash the competition. We have a good, solid product that stands on its own.
• Respect the use of other operating systems. While Linux is a wonderful platform, it does not meet everyone's needs.
• Refer to another product by its proper name. There's nothing to be gained by attempting to ridicule a company or its products by using ``creative spelling''. If we expect respect for Linux, we must respect other products.
• Give credit where credit is due. Linux is just the kernel. Without the efforts of people involved with the GNU project, MIT, Berkeley and others too numerous to mention, the Linux kernel would not be very useful to most people.
• Don't insist that Linux is the only answer for a particular application. Just as the Linux community cherishes the freedom that Linux provides them, Linux only solutions would deprive others of their freedom.
• There will be cases where Linux is not the answer. Be the first to recognize this and offer another solution.

In his interesting paper on Linux advocacy  Joe Barr details the reasons he's no Linux advocate, and the reasons he's not into advocacy in general. Among principles that he proposed I would agree with the following:

1. Don't promise too much
2. Participate in the free source process
3. Offer to help someone start using Linux
4. Consider the other person's viewpoint
5. Donate previous distributions to others
6. Be accurate in what you say

... What really sets them apart is that they stand up in front of people as representatives of Linux, or the Linux community. What they say and do in that role, they are saying and doing on behalf of Linux. That's advocacy as defined in my book -- or, for that matter, in the dictionary, which describes lawyers representing, or advocating for, their clients.

...I do advocate Linux as the right choice as an operating system more and more often these days. In the bad old days, I did the same with OS/2. Further, I have quite often have taken Microsoft to task for its shoddy products and shoddier business practices.

...Secondly, it matters because, when you become an advocate, you lose the right of free speech. As an advocate you begin to speak from a script that you may or may not have had a hand in writing. You begin to lose your own voice, your own style, your own delivery. Everyone you're speaking for is watching and listening to make sure that what you are saying agrees with their take on the party line. Without apology I will say simply that I am not a political animal. Never have been, never will be.