What do you mean, the "Jan San Supplier"? Just curious.
I used various articles on the internet when I first started cleaning. I also drew on my background as a nurse, plus my own years of cleaning my own homes. I made a lot of errors, in the process of learning. Trial and error!! Sometimes making a mistake can be a powerfully good learning experience. As time went on, I gained confidence, which helped me get more (and better-) jobs. At this point I can pretty much pick and choose who I want to clean for. I have found there are a few "super picky" people who are NEVER satisfied with one's work. They always find something silly (or imaginary) to pick on. When I spot one of these, I move on fast. Life is too short to work for people who are never going to be happy with what I do.
This business has its ups and downs especially if you work alone and on a budget. I have learned to roll with the punches and not worry when there is a dry spell. Something always pops up, some great new job.
I have found that owning a super good vacuum really helps impress new clients. I give a demonstration of mine, and watch their faces look surprised when they see all the dirt on the floors under the LED headlight. I have been hired several times simply because of this, as it shows my attention to detail.