I learned canning/preserving food about 5 years ago, which fortunately allowed me to learn correctly without all the monkey's on my back from being in the habit of doing it the "old" ways. But I do remember all my grandmother's annual "canning", but never remembered seeing a pressure canner or anything other than an open kettle. Today I shiver when I think about it. I know of at least one person that obviously was poisoned but I didn't have a clue back then and neither did anyone else.
Perhaps more curiously is that I'm a senior, a guy, and a computer nerd, so canning was the last thing I would ever consider doing, but I won't bore you with a long story. I studied and researched and eventually realized I could answer some people's questions correctly. So I do and that forces me to study and research even more. I never stop trying to learn.
If you ever want to test your canning/preserving knowledge, the National Center for Home Food Preservation offers a free online course through the Univ. of Georgia. Great confidence builder. Go to National Center for Home Food Preservation
and look for the information on the home page. They also have a fantastic recipe book.
The best experts you will find close at hand is the referenced NCHFP website, which is 'the' authority on the subject, and the Ball Blue Book. Between those two you can't go wrong.