Proper etiquette is to wait until your host or hostess has taken the first bite of their meal before you begin eating.
This etiquette rule dates back to a time period before food was refrigerated. The host or hostess would “test” the food to make sure it was safe for guests to eat.
If you are dining in a banquet setting without a host sitting at your table, make sure everyone at your table has been served before picking up your fork.
If you are the one person at the table waiting on your food and the delay appears to be lengthy, it would be polite of you to tell others at the table to not wait for you and begin eating before their meals get cold.