A Question is composed of three distinct parts:
By far the most important is the body of your question because this is where you pose the all important single question that you would like answered. It is the quality of your question body that engages or loses the attention of potential answerers.
You are provided with plenty of space and formatting tools here to assist you to present any background that potential answerers may need to understand your question.
Start by mentioning any relevant background. This saves potential answerers having to try and guess, or to ask, all of which may slow down or prevent an answer to your question.
The question body may well be the only part that potential answerers read and re-read after glancing at the title, so be sure to read and re-read it yourself, and to make ongoing edits to improve it as clarifications are sought by others via comments. You cannot assume that a potential answerer has read any of your previous questions, answers or comments so be sure to include all relevant details so that it can standalone.
Once written, a good cross-check on your question's body is whether it contains a single question mark? If that is the case, then what you are asking is clearly indicated. If you find yourself wanting to place more than one question mark in the body, then questions other than the most important one to you can always be researched/asked separately.
If you are asking a coding question I strongly recommend reviewing How to create a Minimal, Complete, and Verifiable example.
The title is best written after the body of the question because it is there to summarise what is in the body. As a result it should not introduce any new terms or information not covered in the body. By making this as succinct and accurately descriptive of the body as possible you are likely to attract more potential answers than if you hastily pen something like "Help! stuff not working!!???".
My preference is for the title to always end in a question mark because that acts as a constant reminder that this site is about finding answers to questions.
These help the people who are willing to try and help you quickly find the subset of questions in which they have skills instead of having to open many in which they do not.
You can apply up to 5 tags that reflect the significant keywords that are likely to help group your question with others that are somewhat similar.
Do not worry if you get tags "wrong" - they are always quick and easy to fix as incoming questions are triaged as long as the information is in your question body.
What about Comments?
Comments are attached to, but do not form part of, your Question.
Their main purpose is to help you edit to improve your Question by requesting clarifications wherever potential answerers are unsure of what you are doing, using or asking.
Imagine the pleasure of a potential answerer reading just your Question body and thinking immediately "I know the answer to that", and answering it, versus reading a trail of back and forth comments between asker and commenters and thinking "does it mean this" or "does it mean that", and eventually "now I understand" or maybe not, or not bothering to read the comments and just moving on to the next Question.
What about Answers?
Answers should never be written in questions. We have a separate area for answers, and self-answering in that area is encouraged.
Is it OK to greet the audience for my question?
No, there is no chit chat in focused Q&A, and in any event potential answerers are more likely to be impressed by a quick to read and understand question, than a polite hurdle to get past before reaching the detail they came for.
Where do I include thanks in advance to those who may answer?
Don't - that is what upvotes and voting to accept (big green checkmark) are for.
Where do I include my signature and contact details?
Don't - your user card already signs every post that you make and, if you wish, your contact details can appear in that.