Rinse the lemon and remove the sticker label if there is one.
Hold the lemon in one hand and the zester in the other. Now press the zester against the lemon and draw your hand downward while keeping the zester pressed against the lemon.
You should soon see thin bits of lemon peel (just the yellow part) coming up through the holes of the zester.
Remove the zested lemon to a separate dish if it's getting in the way and keep zesting! Remember to only zest the yellow part of the lemon rind, not the white - the white part is bitter and will affect the taste of your finished dish.