After fiddling around with bootloaders and programmers for a few days, I realize there are a few things you have to get right for the whole thing to work seamlessly.
If you do, life is a dream, it all works perfectly and you have a lot of fun.
If not, it can be frustrating.
With a view to helping people who may not realize all the interaction between fuses, clock speeds, baud rates, and so on, I've made a guide to the way the uploading/bootloading process works: