There are many important tasks involved in wedding planning. But the success of your reception can largely hinge on having the right food, beverage, table settings and serving staff. For very small weddings on a strict budget this effort might be undertaken by some friends or family members. But most couples will want to hire a professional. Also, even if a wedding planner or bridal consultant was engaged to take care of things, the couple will still find it wise to be involved in this decision.
Cost and scheduling are the first considerations. The professional selected will have to be able to do the job when you need and within your budget. It isn't necessary to have an exact date and total cost for the first interview. But at least the month, preferably the week, the wedding is to be held is important. Good caterers often book up months, even as long as two years, in advance. Having a specific date is, of course, always preferable. Simply ask if they're available then. Covering cost is critical. It's important to be thorough and detailed. The level of detail need not be granular during the first conversation. An overall estimate of the number of guests and the type of food and beverage desired will be enough to get a rough estimate. That will tell you if you want to continue the conversation.
List as much as possible and review the details when you've narrowed down the choice of caterer to 1-3 companies. Be sure to ask about things like whether linens are included. Find out how much it costs (and how long is required) for pre-set up and post-reception clean-up. Ask how many staff people the cost includes. Compare the cost of sit-down meals with a buffet.