This in no way is a definitive piece of work. I am sure there is much stuff that could be added as well as taken away for some. I am writing to put together less of a "How to..." then I am a "this is my thought process maybe it will help you " sort of thing.
First, No matter how much advice you get everyone will make mistakes! If it is your first or fiftieth feast we all forget something, miss time a dish, have equipment failure etc... Accept it when you start and it will be easier to deal with when it happens. Also in this case when nothing does go wrong you can congratulate yourself on a job well done!
Second, Everyone has a different method that works for them. Find your own method. Take bits and pieces from everyone who has come before you. If they tell you something it is because they have likely been there and done that. If a rigid schedule is your thing, go with it! If you need less structure then give yourself plenty of room to move in. The only "perfect" way is your own way.
On to the beginning...
So, you have volunteered to cook :) Congratulations let the stress begin! Oh, and the fun ;) After the excitement has worn off and you find yourself facing that ever increasing number guests, relax. Take it one step at a time.
I would hope that when you volunteer you already have an idea of what type of event it is. Casual, formal, large, small, intimate, early, late, themed, the list really is endless. If you do not know or a theme has not been set work with the event steward in order to determine this together. Nothing is worse than planning a Norse feast for a 14century English event, or the reverse! Along with theme is know your budget. How much per person, times rough estimate number of people, equals feast budget. Make sure to account for a price difference for children if there is one.
I keep saying "feast" realistically in this kingdom (Drachenwald). This is your "food budget" as most events are all inclusive for food. Travelers fare Friday night, 2 Breakfasts (Sat and Sun), Lunch Saturday and feast Saturday night. If you are splitting the duties with other cooks it is very important that a few things happen. You either need to be in charge of all the money and the purchasing, which would mean getting detailed shopping lists and budgets from your other cooks, or you need to separate the funds into separate pieces for the other cooks to be in charge of. You should always know how much money is allotted to your meals. Both ways have advantages. If you are in charge of all of the food and the money it is easy to slide the 15 euro you are over for breakfasts into the feast budget for an extra desert or to offset a price increase in ingredients. If you have split the budget and the cooking it is harder to have that sort of "play" but it is still very manageable.
Example: your "food budget per adult(14+) is 12 euro and for kids (5-13) 6 euro. You expect 50 people. 36 adults and 14 kids. 36 x 12 = 432 euro 14 x 6= 84 a total food budget of 516 euro. Now if you break this down to meals. you could say Fri night = 1.5 euro pp, Breakfasts 2.5pp euro, Lunch 2 euro pp, and that would leave 6 euro for feast. You could then Multiply by your numbers and get seperate budgets for each meal.
OK, now that we know what type of feast we are looking for and what our budget is the research fun can begin! but that will be next time... this is enough to digest for now.