Sometimes a question is underspecified or ambiguous. Other times a question is fully specified but very long and dry to read. In between there are questions which seem perfect - all the information is there but it's also a joy to read, and makes you want to start thinking about possible answers right away.
Answer with a link to an example question (your own or someone else's) and optionally a brief explanation of why it makes a good example. Then votes will bring the very best to the top, and this meta post can be linked to for examples of how to improve a question when someone posts something too brief or too deep.
This is always going to be subjective so I thought a list of examples might be more useful than trying to define precisely what makes a well presented question. Although there may be overlap, this won't be the same order as the votes the questions have on main, as voting there is also on the subject matter and the challenge itself, not just on how it is presented.