One nice thing with this planning is I can make sure I have scenes in the adventure connected to each character's complications/motivations. To help out with the planning, I made a little Adventure Planning Sheet. Get it from the downloads section at: www.obsidianserpent.com/downloads.html.
This sheet can be used for brainstorming, or virtually the entire adventure plan. When I use this sheet, I still make up the stats for the NPCs, but I usually use my generic NPC cards with slight modifications. The big important set-pieces take a little more planning. I'm now working on a set-piece planning sheet. These big encounters seem to work better when I have already come up with interesting twists and stunts. The planning sheet will help make sure I have everything thought out.
5 Room Dungeon By: JohnnFour.
The Adventure Funnel.
How I GM, Part 1: Plot-Writing.