Remove the pit and scoop out the avocado and place in a medium sized bowl.Mash up the avocados. Depending on how you like it, you make it chunky or smooth.Add the chopped onion, chopped cilantro, chopped Serrano pepper, salt and minced garlic and mix well.Add in the lime juice and mix again.Cover your bowl, we just use saran wrap, and refrigerate for at least 30 minutes. Guacamole is best served chilled and this gives it time for all the flavors to blend.Serve with tortilla chips.