Use a paring knife to slice both ends off of the lemon.
Use a paring knife to slice off the rind right where it meets the white pith.If you cut off some of the pith along with the rind, use a horizontal cut to remove as much of the pith as you can.
Use a chef's knife to julienne the pieces of rind.(Julienne means to cut into small strips.)
Finely dice the strips. The size and shape of the cubes should be consistent.
Notes
The easiest way to zest a lemon is to use a microplane grater.Slide the lemon back and forth along the steel shaft, shaving off tiny bits at a time.The zest will collect in the microplane and you can measure it and add it to your recipes.The reason to use this knife method is:
When you zest with a microplane, many of the lemon oils are released into the air - that flavor is not going into your dish.
With a microplane, you are ripping the skin off of the fruit instead of slicing it. This means the cuts aren't clean. The zest is more likely to stick together in clumps, and this yields an uneven distribution in your food.