Do I "write into the dark" like Dean Wesley Smith, or do I outline my stories like the late Robert Ludlum?
The short answer is: some of both.
Blood Flats was written literally on the fly. I began this book with only the inciting incident and the basic conflicts in mind.
Termination Man, The Eavesdropper, and Our House, by contrast, were all outlined extensively in advance. For 12 Hours of Halloween and Eleven Miles of Night, I used a hybrid method: I plotted out the major incidents of these stories in advance, and wrote the individual scenes "into the dark".
There is no "wrong" way or "right" way in this regard. Stephen King's early novels are incredibly tight and focused, despite being written without an outline. (I can only imagine how difficult the writing of The Stand was without an outline.)
John Grisham, on the other hand, always works from an outline. Grisham has said that he spends more time on the outline of each book than on the actual writing. Think about that for a moment. But The Firm is one of the most original, suspenseful novels ever written.
And yet...herein we can also see the pitfalls of both methods. I love (most of) King's books and (most of) Grisham's books. But as both writers have churned out more work, the inherent weaknesses of their respective methods have become apparent.
King's later works (Doctor Sleep, 11/22/63, Under the Dome) are too long, meandering, and drawn-out. In these books, the tight story structure of The Shining, Christine, and The Dead Zone is missing. I suspect this is a result of King's insistence on "winging it". (Stephen King is opposed to outlining on principle, based on various statements he's made over the years.)
Grisham's work, meanwhile, is sometimes formulaic. Read enough of his books, and you'll start to notice common elements that appear again and again: a hidden pile of ill-gotten money, a lawyer facing a moral quandary, a conspiracy involving government or a large corporation, a race to the Cayman Islands, etc.
I want to repeat: Both King and Grisham are great writers. I recently read (and loved) Camino Road. The point here is not to trash either King or Grisham. The point is to emphasize that a.) if you're a rigid non-outliner, you may develop a tendency to meander too much, and b.) if you're a rigid outliner, you may find, after a while, that you're repeating yourself. (As Dean Wesley Smith has said, your conscious mind will tend to go to the same plots and solutions that it's most familiar with.)