Anything that you don’t remember off the top of your head (probably most of it) or haven’t specifically learned yet, you look up. In terms of knowing which properties to adjust, it’s a combination of looking at how they work differently and just some trial and error.
I typically don’t use a dedicated “cheatsheet” for anything - I just look it up as needed.
Every coding course should be clear about this: nobody expects you to remember the name of the properties, methods, or else before having some years of experience. You should just be able to remember the overall syntax of the language, as well as what is technically possible to do. The rest will come with practice.
Plus, languages evolve. When I started to learn HTML and CSS, grid was not there yet. Now, I can’t live without it, and I’m constantly looking up how to properly use it on the Mozilla dev thingy. My search engine is never used more than when I code. Wether it’s front or back-end code. I look everything up.
At the end, you should check HTML and CSS tags, attributes and properties online regularly, to see if these are not deprecated, replaced by new ones, or what are their support on different browsers for example.
Before I started the FCC courses I had watched some great youtube tutorials from experts like net ninja. They have been a huge help to me and sometimes it’s nice to hear an expert talk and watch them demonstrate rather than just reading everything.