If desired, soak the onions in ice water before adding them to the salad. It's optional, but it takes the strength of them down a notch and prevents them from being overwhelming.
Choose a variety of colors of tomatoes for the best visual appeal.
I recommend using high-quality, flavorful, extra-virgin olive oil. It's such a fresh, light salad so the flavor of the olive oil really shines through. Using a great tasting olive oil will really make the flavors pop and elevate this orzo pasta salad from pretty good to outstanding.