Before we begin…
This forum is not a soapbox
You don’t work for Home Assistant, that’s an open source project. You are volunteering your free time to help others. You don’t have to respond to their rants…
Read the question
All the way through. Quite often the act of writing the post clarifies things in the poster’s mind, so that they only get to the real point in the last couple of lines. There may actually be several questions. They may have got hold of the wrong end of the stick entirely.
Ask for clarification
Do you know what version of HA the poster is using, what their hardware is, what integration they are talking about? Ask to see code, traces, logs.
Are you sure you understand the topic?
If you don’t, or if you sort of understand it, or if you vaguely remember reading something, don’t reply.
Beware of rabbit holes
Reply to the original question, not to the comment before yours.
If it turns out you were wrong, say so
Good practice is to edit your post, striking out the bits that were wrong. This makes it clear what you are correcting. It is customary to add an “EDIT: …” text section to explain what you changed if you didn’t cross out some text.
Begin your answer by quoting the lines in the original post you are responding to
This helps to keep the discussion on track and avoids confusion if there are several aspects to the question.
Stick to facts
No reason why you shouldn’t express an opinion, but if you are, or if you’re not sure, say so.
Link to the docs
Can’t hurt… It can also be quite useful to anyone reading the thread later - the docs are more likely to be kept up to date than posts.
Don’t recommend a YouTube video unless you have watched it yourself recently
They get out of date very quickly and you can’t update them.
Don’t use, or even mention, AI
No, really. Please don’t. See HA AI Help Policy
Be subtle
Not “You should…” but “Have you considered…”, “Have you looked at…”
Don’t be afraid to back off, go silent & get a MOD involved
If you are offended, or the COC or other policy is violated, click the flag button. That’s what it’s for.
Language
Don’t forget that many people are not posting in their first language. Be patient and ask for clarification if necessary. Could you ask a technical question in Polish?
Searching
Don’t make sarcastic remarks about Googling the answer. Searching can be quite difficult if you don’t know the right search terms. Chicken and egg. You can even suggest a link to a search which might have a solution to the question, some people are better in searching then others.
Don’t repeat answers
If somebody else has already made your point, don’t repeat it unless you have something to add. Give them a like! 
If you do have something to add, acknowlegde their contribution with a quote or tag.
Beware of the xy problem
Questions involving unsupported configurations
If the OP has a system that you know for a fact to be unsupported, or they are asking about creating an unsupported configuration, you are better off not replying rather than making their problem worse.
This ‘sticker’ is available if it helps your case.
https://img.shields.io/badge/UN-SUPPORTED-pink.png
