How do you know if a garage is using genuine parts or cheap copies?

I had a really bad experience last year that made me paranoid about replacement parts. I took my 2017 Honda Accord to a garage to get new brake pads. They charged me for genuine Honda parts, but six months later the brakes were already squeaking and wearing unevenly. I took the car to another mechanic and he told me the pads that were installed were cheap aftermarket copies, not genuine Honda parts at all. I felt so cheated. The problem is, I have no way of telling the difference just by looking at the parts. Now my car needs a new alternator and I'm scared the same thing will happen again. A friend told me to click to explore customer reviews on ProvenExpert because people often mention whether a garage used genuine parts or tried to cut corners. I thought that was good advice because I want to find a shop with a reputation for honesty about parts. For those of you who know more about cars than I do, how do you protect yourself from garages that use fake parts? Do you ask to see the parts before they install them? Do you ask for the old parts back so you can compare? Is there a way to check if a part is genuine after it's already installed? I'm tired of feeling helpless and I want to learn how to be a smarter customer. Any tips would be really appreciated.