Want in on the guacamole secret? Add lots of lime (including the zest) and don't over-mash. Great guac must be seasoned correctly, so make sure you have tasting spoons (or chips) nearby and adjust the seasoning as you see fit.
Cut the avocados in half, remove the pits and use a spoon to transfer the avocado to a bowl. Add the cilantro, lime juice, onions, chiles, lime zest, cumin and garlic and season liberally with salt and pepper. Mash together with a fork until just combined. Taste and adjust the seasoning with salt. Store in the refrigerator, covered with plastic wrap, until ready to serve.