Cut the avocados and mash them until they are somewhat creamy. If you want a smooth texture, use a blender or food processor. If you decide to do so then add the yogurt to make a nice blend. If you decide to use a fork to mash up the avocados then you can skip the yogurt. It’s up to you.
Once you have the avocados the way you like them, add the lemon, salt, and pepper. Stir well since you don’t want some parts lemony and some not.
Grate the garlic and dice the onion into small pieces and then add them to the mix. Stir well and taste! If you don’t like your guacamole chunky then put the onions in a food processor along with the mix to get a nice creamy paste. It’s really up to you.