Meal manners entail pacing yourself with others—starting and finishing each course of the meal. I’ve previously written,
At the table, wait until everyone is served. Begin to eat only after the host or the most important guest does. Follow this guideline for each course of the meal. Pace yourself such that you finish at about the same time as everybody else at your table.
A subtlety: if you’re dining out in a smaller group, wait for everyone to be served before you begin. If you’re joining a larger party (say, ten or more,) the “rule of six” prescribes that you can start eating as soon as six people have been served.
At buffet meals, collect your food and wait until three others join you at the table before beginning to eat.