A guest should not have to interrupt the whole table to discover what is in a sauce. For a buffet or potluck, a short ingredient card can make the food easier to approach.
Name the actual ingredients, including packaged sauces and toppings. Keep their labels available when possible. “Creamy dressing” describes texture but says nothing about sesame, soy, nuts, or other relevant components.
Be clear about what you know and what you cannot guarantee about preparation. An ingredient list is useful information, but it is not a promise that cross-contact has been prevented.
Use a serving utensil for each dish and notice when people accidentally swap them. If someone has told you about a serious allergy, agree on a suitable plan with them beforehand rather than relying on a small card to solve every issue at the table.