The "what" piece is obviously what the event is about? This tells you if it is a business meeting that needs lunch catered during the meeting or if it is the type of conference that requires a full service meal. Your meal needs to match the purpose of the meeting. For example, if the meal will be served while people continue to work, finger foods are not a great idea.
The next thing to consider is who will be attending the event. You should consider the nationalities or cultures of the people who will be attending. It is also important to know the level of the attendees. You should have a much different menu for a regular team meeting than you should have if the meeting includes the Board of Directors or senior management. People at the upper levels of the company likely would not think highly of your planning if you choose to serve them pizza or burgers.
The timing of the event is something else that you will need to consider. Keep in mind the season of the year as well as the day, time and how long the meeting will be. If you are planning a summer company picnic, a BBQ or a picnic in the park is a great idea. If it is a meeting to review the previous month and it is on a Friday, you may want to plan a short meeting over cocktails. If the meeting is in the morning, it's probably appropriate to plan for breakfast foods like coffee, bagels or breakfast pizza. Think about when the meeting is taking place before you set the schedule and select the menu.
Where the event will be held is another important component. That may have limitations on how much you can serve or how many different options you can have. Knowing why the event is being held is the best way to set a general theme for the event and the menu. If the event is being done to honor someone for a special achievement or honor, you may want to have a cake of some kind. If it is a mini celebration because of the sales numbers hit by your department, it would be fun to have sparkling beverages (not alcoholic). Fun, finger foods work well for those types of events as well. Knowing how the event will be organized includes understanding the budget and the logistics. This tells you if you are expected to order sandwiches or if you are expected to plan a sit-down, full service meal.