An easy-to-make guacamole recipe is made with 1/4 cup chopped onion, 3/4 cup cilantro and 1 to 3 serrano chili peppers. Chop everything, and mash it all together with a pinch of kosher salt. Dice and mash three Haas avocados, leaving them slightly chunky. Garnish with diced tomato.
The trick to great guacamole is to use ripe avocados. When you press them they should have a little flexibility. If they don't, they aren't ripe yet. Be careful they aren't too soft, which indicates they're overripe. In any case, a taste test is the best way to confirm quality.
To cut the avocado, hold the avocado firmly with one hand and with your other hand use a knife to slice it lengthwise along the perimeter. Open the two halves to reveal the seed. Take the side containing the seed and make another lengthwise cut to remove it or take a spoon and scoop it out. Once the pit is out you can either scoop the fruit flesh out of the rind or take a knife and make cross-hatch incisions, careful not to cut the peel. Then scoop out the pieces gently with a spoon. It's normal for there to be some areas of brown on the avocado flesh, and with guacamole, it won't be noticeable once everything is mashed and mixed.