That would be entirely dependent on the setting, occasion, number of people, and time allotment. You need to be much more specific. There are way too many variables to just put it out like that.
I've worked in many restaurants in my nearly 20 years of experience. Many of which did catering in where I was in charge of, or aided in planning an event, menu, etc. It would sometimes take hours of phone conversations and sit downs with the clients to nail down all the specifics.
I guess the only principle I could give with so little background would be do what makes the customer happy.