I learned from trial and error and also on the job. In my experience, how-tos are typically antiquated or not terribly clear. My best advice would be to dig into ServerFault and Google what you don't understand.
Fun? Yes. Miss it? Fuck no. Recommend people relive the 2012 version of the experience? Huh? Get back to work writing code. Re-read the Wikipedia page on "comparative advantage" first if you need to motivate yourself.