1. Take one. This is not a meal.
2. After taking one, step aside to allow others access.
3. If there are tongs/spoons/toothpicks, use them.
4. Don't double dip, or use toothpicks twice.
5. Make sure your kids observe all the above.
6. If there are others waiting, don't engage the sampling person in long-winded conversation. Especially vital when person is pouring alcohol and needs to pay attention to others who are not you.