A while back I did a major email boo-boo. The result was that every subscriber got the newsletter as well as every other subscriber's email address. Of course, once I realized what I had done, I immediately sent out an apology. One of the responses I received suggested I write a white paper about email etiquette. Please bear in mind that some of what I discuss below comes down to opinion.
Some issues are just common sense while others are a judgment call.
Some people care greatly about these issues, while some people don't see what is the big deal. I think it comes down to two things, how long you've been getting email, and how much email you get. Sooner or later the newbie will pick up some of the more obvious rules. To some people this will seem more like a rant, rather than a white paper. It's not meant that way.