Introduction: I have yet to meet a subject matter that I cannot understand. Writing the document from a technical level of understanding to the target audience is an amazing feat. I prefer learning rather than simply reporting. Presenting complex ideas is great work and, for me, incredible fun.
The challenges:
1. Interviewing subject experts.
2. Gathering information from many sources: people, 'net, 'company documents.
3. Setting and making meetings. Find out all who are involved and keeping all up to date as to status/progress.
4. Hands-on experience: code or hardware, get my brain into it.
5. Write the rough draft.
6. Deliver all copies for review.
7. Gather reviews.
8. Engage a few to discuss additions, changes, updates.
9. Write the document.