Depends how many people are going.
General rule of thumb–for every two people, budget 100 dollars for food each day. (20 breakfast, 20 lunch, 10 snacks, 50 dinner). It might end up being a little more than you need, but it’s always better to OVERBUDGET than underbudget.
Set aside a certain amount for miscellaneous (souveneirs, parking, tips, etc). It depends what kind of person you are, but I would set aside about 25 dollars for each person per day. (to be safe!)
You know how much rooms will cost (this depends where you stay of course!)
Tickets vary with the amount of days, options, membership (AAA, Florida resident?)
Gas or plane ticket? Make sure to budget gas BOTH WAYS
Really those are the main budget sections. You can always throw in an extra 100 just to be sure.
Use Microsoft Excel (assuming you understand the functions and how to use it). It is a wonderful tool for budgeting, trust me! If you need any assistance or further advice, just shoot me a PM. I can even send you a screenshot of my Excel budget I used two weeks ago for my trip (color coded!)