Buy the Park Tool Blue Book. A real paper one. I've had one for ages and still go-to for things I don't do often. Other books are good, too. (Zinn, for example)
Then you just have to start tuning things when they seem off (probably not often) and fixing them if they break (probably rare).
Learn to clean and lube your chain, that's regular maintenance. Learn to change a flat when you only have the road tools from your underseat bag - tire levers, a tube and an inflator.
Learn to really search this forum - I'd guess that 90% of all cycling knowledge is in here somewhere, if you can find it. Do that, so that when you do ask (and you should), some barky dog here doesn't finger-wag ya.
You know everything's right if you bike does what you expect it to and does it quietly.