Combine black beans, corn, onion, avocado and tomatoes in a large bowl. Add most of the lime juice, cilantro, vinegar, olive oil and salt and pepper. Stir gently to combine, and taste with a tortilla chip. Add more lime, cilantro, oil, vinegar, and salt and pepper to taste.
Notes
I never measure any of the ingredients- I start with all of the vegetables, and add everything else and taste as I go. I am always very generous with the lime and salt!