How much research do you do when you write?

Is it fiction or non-fiction? Who’s your audience? What is your goal?

I was starting up an article about Morning People versus Night People and I was going to just jolly along and write whatever I knew about it–mostly that I’m a morning person and that pretty much a waste of time after 3 PM. But a quick search gets me to Morning Person or Evening Person? How your Body’s Clock Affects Your Life. Should I write what I was going to write or read this and then write what I was going to write, but then be a little bit more informed? I suppose the answer lies in what I want to accomplish with my post.