Decide what kind of food you'd like (and have the budget) to serve: a buffet, tapas, a seated dinner or desserts only. Consider food options that will work with the theme of your event. Serving cheese cubes and pigs in a blanket to the Vegan Society is not going to go over well, regardless how much money you save on the catering. But you don't have to provide an expensive four-course meal, either. Make it clear in the invitations what will be served -- even if you aren't asking people to make their selections beforehand -- to ensure that your event won't be full of hungry, angry guests.