Slice each avocado in half, running the knife around the pit and twisting the two halves to open the avocado. Remove pit and scoop the flesh from the skin of each half. Place flesh in a medium mixing bowl.
Mash avocados with a fork or masher until mostly smooth (leave a little chunky if you prefer).
Squeeze in lime juice and add salt, cumin, and chili powder. Stir to mix evenly.
Add chopped cilantro and stir to combine.
Use ripe avocados for the best flavor. Avocados should give just slightly when squeezed gently. Avoid avocados that feel fluid under the skin. A few brown spots in the avocado flesh are just fine and perfectly edible.
Some people claim that keeping an avocado pit in the guacamole will prevent it from turning brown.