The goal is to finely chop or dice each ingredient. This takes a little extra time, but so worth it. For example for each grape tomato, I would cut in half lengthwise, then into 6-8 cuts per half. I find the easiest way to get a small dice on an avocado is to cut it in half lengthwise, remove the seed, then scoop it out and dice it on a cutting board versus trying to score it while it's still in the peel.
If know you aren't going to eat this all in one sitting, I recommend just dressing the portion you will eat and store the leftover salad and dressing separately.