Remove the leaves from the head of cauliflower, then slice the cauliflower into 4 large chunks through the center of the stem.
Using the side of the box grater with the largest holes, hold one piece of the cauliflower at the stem, and grate the cauliflower florets into a rice-like texture. Repeat the process with the remaining 3 pieces, until all of the cauliflower is riced. You'll need to stop grating when your knuckles get too close to the sharp surface, so you can dice anything that is leftover with a knife.
Method 2: Food Processor
Remove the leaves from the head of cauliflower, and cut the caulflower into small florets. Small, relatively similar-sized pieces ensure that the food processor will break down everything evenly, but you don't have to dice it or anything.
Transfer the cauliflower florets to a food processor fitted with an "S" blade, and process until a rice-like texture is achieved. I like to pulse the food processor a few times, to make sure no large chunks remain.
The cauliflower rice is now ready to use! You can serve it raw, like in a Cauliflower Tabbouleh Salad, or saute it for a Cauliflower Fried Rice. Leftover raw cauliflower rice can be stored in an airtight container in the fridge for up to 2 days, or in the freezer for up to 3 months.