I may have to make a page about this, it comes up fairly often...
One thing you want to do, is try to keep costs about the same for everyone. You do this in part by dividing up the various categories differently, for example, meat/ entree for 6, but veggies or potatoes/rice for 10. Thus, you end up with different numbers of sign up slots under different categories.
I also help people out by putting examples under each category.
Here is a sample:
POTLUCK SIGN UP SHEET FOR 100 PEOPLE
Appetizers- 6 items- 16 servings= example 1 1/2 pounds cheese or 1 quart dip plus 18-24 ounces chips, crackers breads
Salad or veggie tray- 8 items- 12-16 servings= example 2-3 pound veggie tray with dip or 2 pounds salad with dressing
Main Course-16 items- 6 to 8 servings= example large whole chicken or 2 pounds meatloaf or 2 impossible pies or quiches
Veggies 6 items- 12 to 16 servings= example 9x13 casserole or 3 quarts/3 pounds veggies
Potatoes/rice, etc. 8 items- 12 servings= example 9x13 casserole or 3 quarts rice pilaf
Fruit- 10 items- 10 servings= example 12 inch fruit tray, 10 pound whole watermelon
Bread 6 items- 16 servings= example 2 loaves French bread, 16-20 rolls or biscuits plus butter or spreads
dessert- 8 items- 12 servings= example a 2 layer cake, 2 small pies, 9x13 cobbler or cake, 24 small cookies or bars.
Specialties- 10 items= please indicate item and amount- remember, everyone will want to try some!
Ice, Non-alcoholic Beverages, Paper goods will be supplied by the hosting team. BYOB for alcoholic drinks.