Add the avocado to a mixing bowl and mash well with a fork

Add in the garlic, onion, tomatoes, salt, pepper and lemon juice and mix well.  If you're not eating it right away, take the avocado pit, press it in the middle of the guac mix, and cover it tightly with plastic wrap, to remove as much air as possible so it doesn't brown as quickly (you can also drizzle some more lemon juice on top to slow the browning process).

Dunk with crunchy tortilla chips or add a dollop to your tacos!