The thing about guacamole is that it’s made from nearly all fresh ingredients, so a recipe isn’t going to be 100% foolproof. You’ll have to make some adjustments depending on how each ingredient in that batch tastes. My tip is this: baby steps. Add maybe half of the fresh ingredients to the avocados and taste the result before adding the remainder. There’s nothing worse than finding out you got a really strong onion or an especially spicy pepper after you’ve added all of it to the bowl. Be sure to taste before you commit! —Kitchenette
Cut the avocados in half, remove the pits, and place in a bowl. Squeeze the juice of two limes over the avocados and mix well. This will keep them form turning brown. Use your knife to cut up the avocados, but leave them in fairly large chunks. They'll continue to break up as you mix in the rest of the ingredients.
Add the rest of the ingredients. Remember to be mindful of the fresh ingredients, they can be potent at times! Carefully mix everything together, trying not to turn the avocados into complete mush.
Taste and add more lime juice, serrano chili, onion, and cilantro if necessary. To store leftovers, or if making ahead of time: cover with plastic wrap directly touching the surface of the guacamole to prevent browning. Refrigerate.