I was wondering what is considered good form for answers for mathematica@stackexchange and consulted the FAQ. It is quite thorough in explaining what makes for a good question, but does not provide a lot of guidance for what is considered a good answer.
Because of how compact Mathematica code can sometimes be, sometimes the best answer is a one-liner, but it seems that those responses usually go in as a comment. On a recent question (Apply a Function Pairwise) I notice the commenter was encouraged to put in the comment as an answer and did so with a little background too which also seemed quite appropriate.
It seems that a code example is almost always a good idea in an answer, so is a little background info, especially for basic questions.
Apologies if the suggestion to flesh out the FAQ with suggestions for answers is covered somewhere I haven't yet discovered :)
(I notice I can't post this with the tag 'faq' so trying something else...)