Gather And Prepare Everything: Place all the tuna, mayonnaise, vegetables, herbs and seasonings on your work surface.
Open And Drain The Tuna: Drain the liquid thoroughly from all four cans before adding the tuna to the mixing bowl.
Dice The Celery: Cut the two celery stalks into small, even pieces.
Prepare The Red Onion: Finely dice four tablespoons of red onion.
Prepare The Fresh Herbs: Chop 2 to 4 tablespoons of parsley, chives and/or other fresh herbs.
Measure The Dressing Ingredients: Measure the mayonnaise and Dijon mustard before combining the salad.
Combine The Tuna And Vegetables: Add the tuna, celery, red onion and herbs to a large mixing bowl.
Add The Mayonnaise And Dijon: Add the mayonnaise and Dijon mustard to the tuna mixture.
Season And Mix: Add kosher salt and ground black pepper to taste, then stir gently until everything is evenly combined.
Check And Serve: Taste the salad, adjust the seasoning if necessary, and serve immediately or refrigerate until needed.