Answer by Robert Frost:

How do you decide what questions you will answer?
When I scan through my A2A list, I'm primarily looking for questions that I think are interesting, that I haven't answered already, and that I know the answer.  Contrary to Quora's new approach, I'm less likely to answer short questions.  I don't like them. 
I'm lazy.  While I like the idea of going off and researching an answer and learning something myself, I'm too lazy (or busy, yeah, that's the ticket) to do that more than once in a blue moon.
Sometimes I'll answer a question solely because the premise of the question is wrong and I feel compelled to correct it.
I prefer to not answer questions that already have answers.  If I answer a question that already has answers, it's because I feel that the existing answers are not satisfactory or could even cause harm.  As an instructor, I can't abide the spreading of bad information.
How long does it typically take for you to answer a question?
As already stated, I'm lazy.  I rarely spend more than a few minutes answering a question.  If an answer takes more than 10 minutes, it is usually because it requires math or needs an illustration.  For the math questions, I open up Excel or Numbers and plug and chug.  For the illustrations I open up PowerPoint or Keynote and doodle.  Sometimes I feel a photo would work best and it can take a minute or two to Google up the right photo and then crop it.
Do you plan out your answers?
My training and experience as an instructor has made question answering a pretty automated process.  I look at a question and think "how would I teach this?"  In the classroom, I know not to open my mouth until my brain has decided what the destination is.  Answers are stories.  Before I start to respond I need to know Act one and Act three of the story.  Act two can develop as I'm talking.  The process is pretty similar when writing a Quora answer.  Before word one is on the screen, I have to decide upon the setup and resolution.  The development, or meat of the answer is largely stream of consciousness.  I often dictate my answers using Siri.  Then I skim through them and try to catch the errors, fix the formatting, and reduce some of the babbling.

What is your Quora answer writing process like?