Have a look at this series of blog posts by Dave Thomas of Pragmatic Programmer, a publishing and training company for programmers.
To start at the top of this 7-part series, scroll to the bottom of this page:
http://pragdave.pragprog.com/pragdave/writing_a_book/index.html
I particularly liked Dave's suggestion to imagine Readers on Your Shoulders as a way to write what your niche wants to read.
Writing Prompt: Read through Dave's description of the hero's journey and how it relates to the journey of programming novice to expert. What is the journey you want YOUR readers or clients to take?