you will not learn everything overnigh as it can take many years to accumulate knowledge. the more experience you get the faster you will learn.
i myself diagnose hardware and software problems on 7 pcs in my local area. i have ran into many problems including hdd failures, ram failures, virus & trojan infections, windows bugs, driver issues as well as quite a number of other factors. compound onto that the issues that i solve here on this website. i may not be familiar with all problems however i try to work my way through them as they occur. i translate this real world knowledge to this website and even for unfamiliar problems or symptoms i often have at least an idea of the cause.
i have been gaming for 14 years. while this may not sound very useful realize that this is a very good way to learn firsthand about display technology. you learn about ghosting, vsync, tearing, bit depth and response time firsthand. there is also some networking and software diagnosing as well when games do not work. from using a keyboard and mouse you can learn the difference between laser, led and ball firsthand as well as the difference between mechanical and non-mechanical keyboards depending on what you use. while not a direct source of knowledge there is alot you can gain from any hobby which relates to computers in some way.
i have an android phone which i rooted and rommed. i started out fresh without much knowledge on the matter however now its not much of an issue and i can give advice firsthand. i know what works and what does not work. i know the safe ways to accomplish things and i know the wrong ways. i have experienced a phone crash and semi-brickup and recovered from it due to the things i learned. i did all of this by reading quite a bit on this (google the topics) and from my own firsthand experiences.
i have built 4 computers so far from parts. doing this many makes it apparent what works and what does not. i also suggest parts on here to use. i do my research into various different technologies when i do. this comes from either working firsthand with the products or brands, various specifications from the manufacturer, professional reviews, user reviews or searching for problems with that certain technology. there are also cases where from my experiences helping on here i have seen various comments stating particular problems which i then remember for the future.
how did i get good enough to co-write a sticky on monitors at the top of perepherals? (you should all check it out). well to be honest i knew quite a bit however while looking up the various technologies i learned alot. i came away with 3x the knowledge i had before. there is no one person which knows everything as that is impossible. what is more important is knowing where to look for the information and what sources you can trust. i went through and read in depth on each technology which was very informative. i have always known the basics of how everything worked however the devil is in the details.
msnbc, tomshardware, anantech and some other tech websites all have some nice good articles on technology.
where else would i have learned that there is a product which can actually make a small mass of metal invisible to the naked eye by bending light streams around a space.
i also learned from other sources such as watching space documentaries even. this is how i discovered quantum computers which use quantum entanglement. an odd source to learn about computing technologies!
in general the more you do in life which has to deal with technology the more knowledgeable you will be. you will learn double or triple the amount if you are directly involved with solving problems or diagnosing issues but in very select fields.
what i mentioned isnt all of my sources however there are just too many to list. honestly this is why i said "a little here a little there" in my first post. there is no one way to get "good"