Take a gantt approach. Use planning\packing for a trip as an example:
- Backpack
- Passport
- Cash (Local currency)
- Cash (Foreign currency)
- Laptop
- Laptop Charger
- Sunglasses
- Sunscreen
#1 is referred to as a Groups of Tasks. a-f are referred to as Milestones or Tasks.
Milestone, a line in the sand when something was accomplished or crossed-off.
Task, a time-frame with a Start and End date. Many tasks can in some cases define a Milestone.
This gives me a method of plotting the outline of the authoring and give me the ability to add things I missed back in later. For example maybe I forgot I would need Sunscreen (g).
At this point you have the skeleton of what you are going to write. Research each Milestone\Task, Use the Tasks to set hard-stop (end date) goals of researching a specific topic or thought. You don't want to be stuck researching a particular thought forever!
Result:
I'm going on a trip to Florida. I don't have my passport yet but will be getting this by the 1st of June. This will go in my backpack (carry on) along with some cash (local), Laptop, Laptop charger, Sunglasses and Sunscreen. On arrival I will stop at the ATM and pull some additional cash (foreign).