This thread is opened for a compilation of exemplary questions of various types, that can be linked as models or advice on how-to-post.
Here "exemplary" primarily means questions that are structurally excellent in ways that can be repeated in other postings, such as motivation of the question, strategic use of bounties, informative discussion of sources, or demonstration of un-obvious difficulties in the question. The specific mathematics within the questions is not as important, though there have been some postings that are memorable simply for the very high quality of mathematics brought to the questions and answers. If the good structural features can be articulated, they can be imitated.
The hope is that examples could replace the presently most common response -- negative criticism, whether direct or implied -- to questions of similar type that lack the positive attributes. There is at least one recurring category of posting (you know which one) where a change from negative to positive replies would be an ecological improvement to the site.