Mix the onions and pepper in with the tomatoes and avocado.
Pour about 1 tablespoon of olive oil into the mix as well. Since we aren't mashing this up into a guacamole, the light coating of olive oil helps to give it that "salad dressing" feel. I would say this is optional, but it really adds nice flavor to the dish.
Squirt! An important element to this salad is the presence of something acidic like lemon or lime juice. Not only does it add a great depth of flavor, it keeps the avocado from turning brown. I like to use anywhere between a a teaspoon and a tablespoon of lemon or lime juice.