In addition to what others have mentioned, I relied on Stereophile reviews and on seeing what gear manufacturers and dealers chose to use at a Stereophile-sponsored audio show I attended. I was fortunate also to know a dealer who sold me his demo units of the amplifier that was used in designing the speakers I bought (and still have). That helped greatly in getting the crucial match between amp and speakers. At a couple dealers I had heard the speakers with other amps, and these amps sounded better. So, I also relied on two high-end dealers whose ears and knowledge I respected to assemble the core of my system.
Is it possible to really know what you're doing?
Somehow I managed to select components that are getting along and feel comfortable with how things are sounding after many upgrades. I rely on others to advise along the way. I'm very good at asking questions.
Every facet of a set up is quite complicated. Even power cord's can be challenging. Name recognition is very important and there are so many names.
The technical aspects of everything involved is clearly overwhelming and requires a lot to barely understand. I've learned enough to know that I really don't understand a lot. At least I'm able to appreciate what I'm listening to which is all that really matters, and know if something sounds good.
Just my thoughts for what they are worth.