Sometimes I looked at institutional websites. You can find precise information about what documents you need to present, for example, but not very much else. Personally, I have always prefered to actually go to the different offices, to talk directly and hear in person what I had to do. Even though the laws are national each Prefecture applies them differently, with nuances and idiosyncrasies that you won’t find online.
When you telephone, the person who answers doesn’t have the time to answer correctly. It’s as if you are disturbing them and preventing them from doing their job. You get imprecise, or even completely false, answers.