There's that white page. What am I going to write on it? The blinking cursor waits and time moves on. I close my eyes and start typing. I can see my hero and my heroine--shipwrecked...on an island with a white sandy beach...
This is going to be fun!
That white page can be daunting, but authors are brave souls. However, they use different methods to get their books written. Some are methodical. They are the plotters. Then there are those who just sit down and write. Those are the pantsters, so called because they wing it--flying by the seat of their pants, or in their case, writing by the seat of their pants.
There are some writers who employ both methods.
Much has been written on this topic and you can find plenty of other blogs covering this subject just by typing pantster vs. plotter into Google.
As for myself, I have used outlines for several of my books, but I have often wandered away from my original plans. I have written some books completely by the seat of my pants--winging it through the manuscript. When I use that method, I have a lot more fun but I tend to go off on tangents. That results in more editing when all is said and done.
Nevertheless, I always have the story in my mind even if I do not have a detailed outline. I know the main characters, the main conflict, and the setting. It is quite an adventure to set sail without a script.
A brief survey of my Twitter friends indicates the pantster method is alive and well.
Mia_Marlowe @penelopemarzec Definitely a pantster. Once I figure out who my characters are and what they want, keeping them from getting it is my plot. 
suzannelazear @penelopemarzec I'm actually a puzzler with pantster tendancies. 
LdyDisney @penelopemarzec Pantster! :) 
freyasbower @penelopemarzec pantster all the way. (g) Some of my Facebook friends chimed in, too.
Nancy Sue Petersen Brandt I'm a pantster trying to reform!
Catherine Guerrero I'm a pantser and proud of it. Got my rough draft for a new novel started that way back during NaNoWriMo.
I believe using the pantster method is rather like recording a dream while being awake. To do it, I must turn off my internal editor. Then I just let it rip.
Are you a pantster or a plotter or a little of both?
