When it comes to grating citrus zest with a rasp-style grater, many people tend to hold the grater steady while moving the fruit back and forth over the grater (just as most other graters are used). But there's a better way: Hold the fruit steady and move the grater over the fruit, as you would a file.
This approach offers two advantages. First, holding the grater this way allows it to helpfully collect the zest rather than scattering it below the grater. And second, you can see exactly where the grater is contacting the fruit, so you don't accidentally hit the same patch twice and grate bitter white pith along with your zest.