Did you know it is proper dining etiquette to pass them together even if the request is only for one? These two are essentially married to each other and should always be passed together.
Additionally, you may want to taste your food first before asking for the salt or pepper. The chef could feel insulted that you assumed the dish wasn't seasoned to perfection. Honestly, this bothers me quite a bit. Please taste my dish before you reach for the spices.
And here's a tip... keep this in mind during a business luncheon or interview as well. If you taste your meal before seasoning, this act gives a person insight into your decision making. You appear to gather information before making a final decision. Never assume.
So, please don't orphan your shakers. Pass them together!