If there's guidelines for asking questions, there should probably be some guidelines for providing answers. To this end, what do you think we should say?
Edit: I've also suggested this item for inclusion in the FAQ. Feel free to upvote/comment the answer there, but please continue to use this thread for discussion of exactly what the "answer guidelines" should be.
Apart from any other guidance, we should have some specific guidance on how to answer subjective questions, which are usually looking for experience or opinion. We could import wholesale the original "Back It Up" principle that motivated the "Good Subjective, Bad Subjective" article:
Subjective answers should be based on:
Something that happened to you personally, or
Something you can back up with a reference.
Or we could develop something along those lines with language more specific to our context.
Don't post an answer that is the similar to one already posted, unless your answer has significant differences or includes a notable amount of additional detail.
For questions regarding game rules, include references to official content if available.
(I have to remind myself of this one sometimes.) While voting and reputation are a part of the way this community operates, answering is not a competition. Keep it civil and objective.
Answers to the same question should not refer to one another. Each answer should be full and complete in itself. If you are building upon another answer, quote it in full in your own answer.
If a conflicting viewpoint needs to be addressed as part of an answer (see bullet 3 first) the address that viewpoint within your answer. Do not address other answers representing that viewpoint, or their authors.
Answers can, and in many cases should be edited. Any time there can be changes made for clarity, or if you find an error in your own answer, by all means edit it! Also, bear in mind that some answers may need to be changed over time due to rules updates, or even edits to the question itself.