I stumbled (happily) into the world of Japanese style gardens while working at an Arboretum in Canada, where they were building one while I was a summer student working there. Then, after completing my horticulture training, I worked at the same arboretum and had to figure out how to maintain the garden (one of many I took care of). That led me to the advert. for my current position, for which I was accepted because of my intense horticulture training at a renowned school of horticulture, not for any knowledge on my part about Japanese gardens. I still don't know what I'm doing, but I know more than the rest of my colleagues, so that makes me the resident "expert." I've had to learn through trial and error what works with the plants and pine trees in my care and what doesn't (yeah, I've killed a few things along the way, but to my credit, I have not killed any pine trees that weren't already on their way out). So, if anyone wants to know what NOT to do in certain situations, I'm your gal!
Seriously, though, I've had to teach myself pretty much the whole way along. I was lucky enough to go to the Kyoto seminar and we have a well-stocked library here which I've mostly worked my way through. I've had to figure out the history and design aspects for myself, since I have no formal training in either. Luckily, there are a number of very friendly experts out there who are willing to pass along their advise and experiences to us beginners.