I have three favorite approaches to starting a fairly lengthy writing project. Note that there is a crucial step prior to any of these three prompts, and that is to create an outline (to be discussed thoroughly in a different article). Once you have an outline, you still have to sit down to write, facing that proverbial “blank page.” Here are some tools to make getting started so much easier.
Conjuring up your intended reader and what questions they have (about your topic) is one of the techniques which will PULL words out of you. First, describe and define your target reader. Then brainstorm to come up with at least 25 questions they may have. You aren’t deciding to write about and answer all of these, these are just to create prompts.
Another strategy that works well in some cases is to “begin with the end in mind.” What do you want to leave your reader with? Start 
writing your summary, first. This can really help you focus as you write the whole piece.
Once you have an outline, it’s fine to use the approach “just start anywhere!” What is foremost on your mind? What story or example is fresh and vivid? What are you charged up about at this moment?
The mood to write will always ebb and flow, so you want to have tools like these three strategies handy to help you engage when you have the time or necessity to write.
Did you know that Barbara Dee teaches nonfiction writing? Contact her to find out more.
