Find a rock or piece of concrete with a round divot.
Place the macadamia nut in the divot.
Locate a large rock or hammer.
Bang the nut with the rock until you hear a sharp crack. Make sure to start out soft and get progressively harder so as not to smoosh the delicate nut meat.
Peek away the cracked shell to expose the nut meat.
Extract and enjoy! They are delicious raw, and equally delicious roasted.
To save time, crack a bunch at once, and save the labor of extracting the nuts until later.