It's also taught me how to use preset stop-down lenses. These are lenses with 2 aperture rings -- one that clicks and sets your minimum aperture, and another non-clicking ring that actually controls the aperture. The point used to be that if you wanted to shoot at, say, f/8, then you could set the clicking ring to f/8, and then set the controlling ring to wide open (in this case f/2) so you'd have the most light for focusing and composition. Then when you're ready to shoot, you could quickly turn the aperture control until it stopped at you desired f/8.
That aspect is anachronistic for most of us, but I've found I really like it otherwise. Most modern manual lenses have clicking aperture control rings -- the advantage to clicking in place is that you can be sure of the exact aperture and you're less likely to accidentally change it. But one disadvantage is that you usually can't set it between stops (say at f/3 or 3.1 ish). And if you're shooting video it makes it tougher to change the aperture during the shot because of the lens vibration of the clicking, as well as the noise if you're also recording audio. This is why you'll see some hacked "de-clicked" lenses out there. This double-ring setup (which still exists on a few still-in-production lenses such as the Helios 40-2 85mm) gives you the best of both worlds -- smooth aperture control with one ring and the exactness of a click-stop with the other.