1. Foundation First. Get and idea and map it, that is the base.
2. Determine major players, their roles, interactions and motivations.
3. Nuts and bolts, what are the forces and industry etc. as well as opposition groups and social fabrics
4. Mileposts and Goal. Where will the main arc end up and what are the major events along the way.
5. Start from there and keep detailed notes so as not to contradict and to provide possible threads for later use.
6. Be willing to modify or ignore milestones, or add new ones, as the story grows.
That's the basics I follow.
