As Larry linked, there are loads of free resources available from the government and various universities. The Ball book is also excellent.
You need to understand that one method does not work for all things. High acid foods like tomatoes and many fruits can be safely canned using just a hot water bath, but the vast majority of foods must be pressure canned to ensure all bacteria are killed off and the food is safe. This is not something where you want to just wing it. Botulism is exceedingly nasty and can cause permanent organ damage, assuming you survive at all. I don't mean to scare you, but just be aware you need to follow instructions carefully.
I think most people start with the simpler things like tomatoes and pickled peppers. You can get the necessary equipment at most hardware stores and it shouldn't set you back more than $40, not counting jars. If they find that rewarding then they'll branch out into pressure canning. A good pressure canner is expensive so this approach makes sense. Canning is a LOT of work so you should be sure it's something you want to pursue before spending a lot of money on it.
As to canners, I personally prefer the All American pressure canners from Wisconsin Aluminum Foundry. They are exceedingly well built, looking like they'd be more at home in a laboratory than a kitchen, and do not require a gasket. This can be a key thing because pressure canners will last for generations if properly cared for and gaskets are wear items that can be very difficult to find decades after the canner has gone off the market.