I like to buy organic fruits and vegetables, but there are sometimes when it matters more than others. If using citrus zest, it is worth it to get lemons, limes, oranges, and grapefruit that is free of contaminants.
When zesting, I like to use a fine microplane grater, which is a readily available and indispensible kitchen tool. You want only the very outer layer of the citrus. Do not go so deep as to get the white pith, which is bitter and lacks flavor.