Stephen Anderson:

So when is the best time to write a book (or give a presentation or start a blog or…) on a subject you’re particularly interested in? While you’re learning! Putting words on a page isn’t a commitment (trust me). You’ll be able to add to, edit, and refine your ideas along the way–but only if you take the time to write them down. Also, there’s a certain amount of fidelity to your thinking that fades over time; write in the moment and you won’t lose the burrs and barbs that stick with readers.