I create a rough outline, one or two sentences for each chapter or major event I have "planned" and each has a check box. Then I leave checkboxes in the space between each with nothing written ( these will come.) I have the general idea of whats going on but those blank spaces are always a suprise. I pick a "random" box to check, write the chapter. Pick another box elsewhere in the story, write it, and then start to connect the dots and blank space. I'll have chapters 1-3, 5, 14, 20-25, 32, 40. Then jump in between each whenever I have a new idea about how to tie them together.