Structure the question entry form so the asker is forced to organise the question in the clearest way possible. This means moving away from just having one big text entry for the whole question, and instead splitting it up into several entries, like the following:

• Problem statement--executive summary
• What I expected
• What actually happened
• How I tried to solve the problem (and any research that I did)
• What I need answered (i.e., any answer that addresses this section fully will have the sufficient criteria to potentially be accepted)

Make all the entries mandatory. Question can't be posted until all of the above are filled. If any of the above is filled with nonsense, let a moderator immediately and mercilessly close the question.

The above is heavily influenced by Jon Skeet's post on composing a good question. Hell, just link to that post from every question entry form.