A brief note on two important parts of MSE
While you're attempting to participate on any question in this website in any role (as the OP, the answerer, a visitor, a curator etc.) focus on the organization of the website (around that question) and the reliability with which that question can be addressed. One paragraph on each.
"Organization" refers to the ease with which one can search and find the best possible questions and answerers corresponding to one's true mathematical purpose on this website. Kindly attempt to perform actions that aid the organization of the website. For example, edits improving MathJax, and converting images to readable text are two ways of aiding organization. Answering duplicates, and wrongly tagging questions are two ways in which hindrances may occur.
"Reliability" refers to the addressal of a question "beyond doubt". Kindly attempt to take actions that aid the reliability of yours, or others' content on this website. For example, clarifying definitions and requesting for context in comments are positive actions, as is the action of downvoting mathematically incorrect answers. On the other hand, writing speculative answers and up/downvoting answers based on reasons such as grudges against the user providing the content compromises the same reliability.
MSE stands on the pillars of organization and reliability, and I believe our actions as users here should serve these purposes.
If you wish to answer a question,
This is your general guide to answering a question properly, so that one may call it a product of "quality". It's a short read, do look through it.
Avoid answering duplicates. See this for how you can search on this website. Approach0, use MSE search properly, use the meta-collection of duplicates , are three of the suggestions there. Duplicates are not merely better for organization : a high quality answer should not appear after a low-quality answer to the same question on a search, and a small number of duplicate answers prevents this from happening. $94$% of users come to MSE after a referral (as per the mod tools), so this has to be respected.
If context is lacking to the extent that it affects your reliability in answering the question impeccably, then request for it. Use this post to help users fulfill these needs so that you can reliably address their concerns. To put these needs in the order I would prioritize them : see if there's a well-defined or accessible source, see if there's background or motivation present in the question, then see if there is an attempt on the question whose answer is requested.
In conjunction with reliability, note that opinion-based questions are rejected on the basis of them not admitting reliable enough answers. See this if you wish to judge such a question. Basically, if you see a question that you can only address with speculative opinion and not back it up with concrete mathematical facts, kindly refrain from answering it.
This answer on the general meta explains why it is important for the sake of organization of the website that only one question is typically contained in a post. Kindly refrain from answering questions where you see more than one unrelated question in the post, or request such users to trim their question and reap the mutual benefit. Such questions are referred to as "broad" for the purposes of closure/reopening.
Avoid off-topic questions. See this for an idea of what is allowed, somewhat okay, and not allowed on this website as a question. While borderline off-topic questions are fine, it is a waste of time for users to ask clearly off-topic questions here if there is another place where their (and visitors') time and effort is invested far better.
If you wish to ask a question or help someone improve their question
Along with How to Ask A Good Question which is a comprehensive guide to improving one's question,
this and this post are more pointed versions of the above post. They can be used for direct instruction to answerers, especially when one thinks the user needs a short introduction. You can use these to optimally design your questions as well.
This is the general MathJax guide You can link this to other users in the comments, who may need it sometimes if their post has unreadable mathematics, or use it in your own questions if you need it e.g. for commutative diagrams or matrices. Check out Short and helpful advice on using MathJax for users who are beginners.
This can be used as a good comment template to assist new users in beginning the improvement of their question. That entire post is full of templates for various purposes, ranging from MathJax editing to titling questions.
You should still read these when you can
This is the FAQ. Please go through it completely when you have the time.
- Linked with the "How to ask a Good Question" guidelines is the Enforcement of Quality Standards(EoQS), a move by the moderators to actively enforce the guidelines. While this has some vocal disagreement, it both should be read and acknowledged as something impactful.
This is the guideline for context edits and rewrites If you wish to add context to a question to salvage it and prevent content from getting deleted, then you may use the following guidelines to edit the question appropriately.
These is the reopen request thread If you have concerns regarding the closure or deletion of a particular answer, you may voice your concerns here. Users will respond to the request by taking appropriate action.
Here are the mathematics chatroom guidelines These are for participation in the "Mathematics" chatroom. You can refer users here if their post is off-topic but suitable for discussion in chat.
Here are the guidelines for reviewing questions. As a high-rep user, I would suggest those who can to review questions and use stronger community actions to run this website.
Some other important threads
This was the thread for the last election, held in $2021$ Here, you will find what questions were deemed important enough to be phrased to moderator candidates. This reflects the "current affairs" of MSE in some sense. You can also check out the comments to see which concerns were raised there and how they were responded to.
This and this are a list of softwares that convert images to LaTeX (the the best of their efforts). These can be used for editing questions.
I'll mark this community-wiki, and others can feel free to edit in some important threads which I may have left out due to my implicit biases.