How do quality large prints get made?

[chauncey]

But don't you find that limits you somewhat in what subjects you can shoot?

Of course...one needs to get close enough that your subject more than fills the frame.
Easier with landscapes...harder with hummingbirds.

[Spam]

I am trying to digest everything you've said and may very well come back with questions regarding "upsizing" that software does after I do a bit more research.

Terri, it might help your searching if you also look for "interpolation", which is a more specific term for upsizing. Remember also that it involves adding pixels to an image which weren't there previously. Photoshop's algorithms do a pretty good job of this, but the result is always going to be limited. Also, if you are using Photoshop to take, say, a 100DPI image to 240DPI, it's better to do so in increments (100 to 150, 150 to 200, 200 to 240) rather than in one go.

That said, I've used interpolation only for pics that are destined for off-set litho printing (newspapers, magazines and posters). I haven't used it for large-format photographic prints.