First, consider the time you will be holding your party. If it is near the dinner hour, your guest may be counting on appetizers for their meal. In this case, plan for eight to 10 pieces per guest. If your party is midafternoon, six to eight pieces per guest is about right.
If your guests will be mostly men, make a little extra—men simply eat more.
And if you expect that your guests will consume a lot of alcohol, increase the number of appetizer servings per person to 10 to 12—when guests drink, they tend to eat with abandon.