The three keys that do 90% of the work
Mac and Windows keyboards have the same modifier keys; they just wear different names. Learn these three swaps and most shortcuts fall into place.
People expect the Mac keyboard to be a foreign object. It isn't. It has the same modifier keys as a PC keyboard; they're just named and placed a little differently. Three swaps cover the vast majority of shortcuts.
1. Ctrl becomes Command
The big one: Ctrl becomes ⌘. Command sits right next to the spacebar, where your thumb naturally rests, and it does what Ctrl did on Windows.
So copy is ⌘+C, paste is ⌘+V, save is ⌘+S, and find is ⌘+F.
2. Alt becomes Option
Same position, same role: Alt becomes ⌥. As a bonus, Option is also how you type accented and special characters: hold it while pressing a letter.
3. The Windows key becomes Command (and Spotlight)
The Windows key's jobs scatter a little. Searching and launching apps (the Start menu's main purpose) moves to Spotlight: press ⌘+Space and start typing. Locking your screen and opening settings move to Command-based shortcuts too.
The Mac does have its own Control key (⌃). You'll use it occasionally (right-clicking, Mission Control), but day to day, Command is the one your thumb wants.
That's genuinely most of it. Spend two minutes letting these three swaps sink in, and the rest falls into place on its own.