The Trickle - Shall or Will?

Which word?

I frequently use 'shall' and 'will' interchangeably. I've started to wonder if I, as a word usage role model, should be doing that. I meant to look it up the day I thought I could be incorrect. It's taken me several days. Here goes... I start with the Associated Press Stylebook. Few references are used more frequently in my line of work. "Use shall to express determination." I suppose that's why MacArthur used 'shall.' Now I know. Unfortunately, that seems to limit the length of my current blog. Maybe I should go into detail as I look up the spelling of interchangeably. Hmmm. A short side trip. I'd hate to classify myself as a word usage role model and have spelling mistakes in that entry. That self-classification angle gives me another idea for stretching the length of the blog. I once gave myself credit for being "professionally nosy." I was asked what I meant by that. Well, I get paid to look into other people's business. I thought it was pretty simple. That's it. Out of ideas.