I would say that similar to what happens elsewhere on STEEM, Musing's user etiquette falls into the following list of strong preferences:
DOs
—Be original. Don't copy and paste answers from other sources, and don't copy someone else's questions. If you can't think of anything on your own, or have a hard time expressing it in English, maybe musing isn't the best fit for you right now. People will notice if questions are worded the same way, and a quick search on Google will reveal whether the answer came from somewhere else.
A way to avoid asking a question that has already been done is to type what you would like to ask into the "Search for a question" text box in the upper right hand corner of this page. If you find topics that are similar, find a different slant to take. As a matter of fact, this question has been asked before, just not word for word.
—Write questions that invite meaningful answers, personal opinions, and debate. The idea is to provide thought provoking topics for other users to use their critical thinking skills. The questions don't need to be controversial, but something that others will want to answer because they have strong feelings about them or experience with.
In addition, be genuine. It's okay to ask personal questions, even if they don't have broad appeal, as long as they are questions you want answers for. Musing is about helping each other, too.
—Answer the question. Stay on topic. Cover it. You shouldn't write just to write, but you should try to come at a question from all pertinent angles. In some cases, there are questions within a question, whether they are expressed or not. Sometimes answers need to be explained. Go ahead and do it.
So, a few lines of text may be all that's needed with some questions, but in other cases, much more would be appropriate, and welcomed.
—Be polite. For whatever reasons, it's easy to write questions or answers that can be offensive, defensive, or off putting. There's no reason to take things personal to such an extent. Not everyone has the same life experiences, knowledge, opinions, etc. Just like life, Musing would be pretty boring if such were the case. We don't have to agree, but we should at least treat each other with respect. If a question bugs you that much, maybe it's better to move on, or come back when the answer can be answered with decorum.
There's nothing wrong with passion, but there are many ways to express it where people can feel it, maybe identify with it, but not feel like they were beat up or ran over in the process.
DON'Ts
—Spam or plagiarize. I've said be original already, but I think it bears repeating, especially since there has been plenty of it on Musing, and elsewhere. Just be honest.
—Try too hard. If you know an answer, go for it. If you don't, there's no need to fake it. Move on to something else.
—Expect tons of upvotes/engagement. This actually works for all of STEEM, but especially here. Musing's largest delegation was removed, so where it had been upvoting a lot of the questions and most of the answers here, that has not been the case for a while. Maybe Musing will start again. Maybe it won't. Asking or answering questions because you enjoy it will probably be the best way to use Musing regardless of whether or not rewards are involved.
CALLING IT
I don't think this is necessarily an exhaustive list, but it's enough, I think, for users to get as much as they can out of the Musing experience.