I tend to outline my stories as in that I know what will generally happen in the plot. I know who the characters are and what is driving them and what the milestone scenes are. I do not plan every single scene, though and I usually do not write down any outlines. I keep the ideas in my mind and play around with them, altering the details of the next few scenes as I go. Since I know what the next milestone event will be, I can write towards it.