Who is it about?
When did it take place?
Where did it take place?
Why did it happen?
All five are important, but which one do you tend to give priority to?
For me it's usually "Why". I find the motives and precursors for a situation very interesting. It seems like the most unpredictable variable to me, since thought processes between people can differ so greatly.
Perhaps it doesn't really matter in many cases, but it's fascinating to be able to deconstruct a situation down to cause and effect.