It depends on the circumstances - if I'm eating at home or out with friends or family friends, we use our own chopsticks for both eating and self-serving from the dishes.

If we're out with new people, strangers or the dinner is a little more formal, we'll either request extra chopsticks for serving or have the wait staff bring serving spoons if none were included with the dish.

Raw food (except sushi/sashimi) is always handled with a designated set of chopsticks to avoid cross-contamination.