Do you have any sort of synthesis of the core ideas or principles or best practices that work for you?

I think it’s hard to give some sort of master theorem because it really comes down to what you are doing.

That said, start by considering ownership. As you start, avoid creating types with non-static references inside of them i.e. keep to types that own their contents. Types with references requires you to use lifetimes and you’ll be better off getting used to that later. And frankly, it’s often not necessary. The vast majority of the types you’ll ever make will fully own their contents.

Now when you make functions or methods, think of the three options you can use when taking parameters:

1. Take ownership, i.e. MyType or self for methods. Use this if your function needs to own the data, often because it needs to take that data and put it into another value or otherwise consume it. Honestly this is the least common option! It’s quite rare that you need to consume data and not let it be available to anyone else after the function call.
2. Take a shared reference i.e. &MyType or &self for methods. Use this is your function only needs read access to the data. This is probably the most common case. For instance, say you need to parse some text into some structured type; you’d use &str because you just need to read the text, not modify it.
3. Take a unique reference, i.e. &mut MyType or &mut self. You’ll need this if you want to refer to some data that is owned elsewhere but that you need temporary exclusive (unique) access to, so that you can modify it. This is often used in methods to be able to modify private fields of self for example. You need to think about the fact that no one else can have a reference to the data at the same time though. Often this is not a problem, but sometimes you need to be able to mutate stuff from multiple different places. For that, you can consider either passing ownership around, for instance via channels and sending messages or you could reach for Arc<Mutex<T>> to allow mutation through shared references with a tiny bit of runtime performance cost.

When you think in terms of ownership, the borrow checker becomes easy to understand. All it’s doing is checking who owns what and who is borrowing what owned data from who and are they giving it back when they said they would?

I hope that helps but again, it’s a very general question. If you give me a concrete case I could also give more concrete advice.

PS: Abso-fucking-lutely just clone and don’t feel bad about it. Cloning is fine if you’re not doing it in a hot loop or something. It’s not a big deal. The only thing you need to consider is whether cloning is correct - i.e. is it okay for the original and the clone to diverge in the future and not be equal any more? Is it okay for there to be two of this value? If yes, then it’s fine.