Karen, this is really easy

1 can beans (black, kidney, garbanzo, white, whatever)
1 can corn
1 can rotel or diced tomatoes (10-15 ounces)
1 chopped red onion
2 Tablespoons lime juice (don't like lime? use lemon)
1 Tablespoon olive oil
1 Tablespoon vinegar
1 teaspoon salt
1/2 teaspoon pepper

If the tomatoes are seasoned, you can cut out the salt and pepper.

Drain and rinse beans and corn. Drain tomatoes.
Mix all and chill.

Serve as is.
Serve over a bed of lettuce.
Serve over a bed of couscous.

Add other vegetables that tickle your fancy. Cucumbers, peppers. Sprinkle feta cheese on top.

For the purist, you may use dry beans and cook them, you may shuck the corn from the cob and you may use fresh tomatoes.