When the center diff is locked (4hi or 4lo), you'll feel it binding a little bit when making a tight turn in a parking lot. In general, letting it bind up isn't a good idea, that's why they were saying earlier not to drive in 4x4 on the pavement. But, letting it bind just for a second just to make sure the 4x4 is working is a good idea so you don't have to wonder if you made a bad deal the whole way home.
You mentioned earlier about leaving it in AWD mode all the time like your CR-V is. This is not a good idea because you will put unnecessary wear on several components and your mpgs will go to shit. The '01 4runner's 4x4 design isn't intended to be "full-time" like the CR-V's, but rather it's to be used in situations like patchy ice - when you have good traction 95% of the time, but a few rough spots here and there. Here's a little summary of when to use what:
Dry or wet road - 2WD
Wet slick road, gravel, or patchy snow/ice - 4hi unlocked
Packed snow/ice, dirt/mud, or deep gravel - 4hi locked
Deep snow or mud, steep dirt/snowy/muddy hills, rock obstacles, etc.. - 4lo locked