Make your travel arrangements. This is the wild card of your budgeting battle. Typically you will probably either fly or drive. Costs will vary from where you are in the country, especially if you drive. This element alone can put you over the budget depending on the size of your family and where you are traveling from, so be sure to consider different options.
Shop around for airline tickets using travel websites like Orbitz and Travelocity if you decide to fly. You can also sometimes get good deals on packages including hotels or rental cars. Check from several different airports if you are close enough to drive to them. For instance, you may live in Boston but you can potentially find cheaper tickets flying out of Providence.
Figure out whether you want to stay in the Disney Resorts or in a local hotel. You can get good deals either way so look at both. If you find cheap enough park tickets, staying somewhere other than the resort is probably going to be cheaper. There are hotels on Irlo Bronson Memorial Highway in Kissimmee and on International Drive in Orlando that offer transportation to Disney World as part of your hotel price.
Make an itinerary for your park visit. Having an idea of what parks you want to visit on which days of your vacation is absolutely necessary to getting the best price on your park tickets. There are four major parks plus the extras such as a water park and the Wide World of Sports complex.
Decide what kind of tickets you need. There are two basic options; base tickets and park hopper tickets. Base tickets will allow you to visit one park a day and park hopper tickets will allow you to visit all of the parks on any given day. If your trip is short you probably should consider the park hopper tickets to see everything. If you are staying for at least four days, you can see each park with the base tickets and save some money.
Purchase your tickets from somewhere other than Walt Disney World. You will be able to find cheaper tickets from travel agencies and online vendors. A consideration for strong-willed travelers is to attend a time share presentation in Orlando. There are many opportunities for highly discounted tickets if you are willing to sit through a fairly lengthy sales pitch. Be forewarned, though, that sometime the time share presentations are very pushy and you will have to say "no" a lot to get your discounted tickets.
Eat at the hotel and bring your own water and snacks to the park. Food in the parks is fairly expensive, and not budgeting this can put you over your limit. If you have a hotel with a free continental breakfast, take advantage of it. Also carry granola bars, fruit snacks, bottles of water and any other refreshments in a backpack to have while you enjoy the parks.
Buy your souvenirs somewhere other than the parks. This may seem cheap, but picking up memorabilia from Wal-Mart can save you quite a bit of money. Think about buying souvenirs in advance for children and packing them secretly so you can give them to your kids while you are at Disney World.