Pack just enough for you (and family or friends if you want) because buying a bag of chips or soda is wasting money on things that are much cheaper out side the park. But do enjoy some of Disney's special things like pineapple ice cream in the Magic Kingdom, and the various African dishes in Animal Kingdom.
2. Manage Time Wisely
As I've found out the hard way it is a time killer to constantly be moving from park to park because of fastpasses. Try your best to stay in one park for the moment, hit all the rides you want and then move. DO NOT TOTALLY MESS UP YOUR SCHEDULE TO FIT IN A FASTPASS. You are better off waiting in line for 45 mins then spending that same time on a bus, boat or monorail. This also leads to another topic....
3. Manage Your Fastpasses Wisely
If you get one for a ride and come back to that same ride where the wait is 30mins or less or the line is way inside the building, don't use it. Save it for later, perhaps if you get off that ride and want to go again, you can use that Fastpass! Or if you have to choose between getting a Fastpass between two rides choose the one that is newer or is more extreme. Generally they get more visitors. Also please read the times you are supposed to come back, and check the next time you can get a Fastpass. You have no idea how annoying it can be to see a large group or family go to a Fastpass booth and insert their ticket 5 times and get the "This is not a Valid Fastpass" back. It wastes time, money, paper, and patientience. Or have that same group go right to the Fastpass line and be told it's not their turn for another 3 hours, and then block that entrance.
4. Plan what rides you want to go on.
Planning can be done months before you go or as soon as you get that park map. The earlier the better, just make sure you include travel times between parks. Choose what rides you want to go on, and split how much time you spend in that area. It might be a little tedious trying to plan your trip to the world's largest theme parks, but it makes the time more worthwhile.
5. Know the Travel Times.
Ok here are the safe time assumptions you can make when choosing to take Disney Transportation:
Anywhere via bus: 10-20mins
Anywhere via Monorail-5-10mins
Anywhere via Boat: 10-30mins
However the real killer is how long you wait for these items of Transportation:
Waiting for the bus can take up to 20 mins, and it gets longer when loading/off loading handicapped passengers.
Waiting for the boat takes about 5-20mins depending on how many are in operation, and how long the captain decides to stay at a port.
Waiting for a monorail should only take about 5-10mins, being as fast and efficient as they are.
6. For people who don't live in Orlando, Stay at a Disney Hotel.
Yes they are more expensive, no they don't always cost an arm and a leg. However they are convenient, are usually high quality, and you can either get in a selected park 1 hour early, or stay about 3 hours longer. Thanks to the Extra Magic Hour. With free transportation to any Disney park, waterpark, and Downtown Disney. In fact you could come to Orlando and never have to leave Disney Property and still have everything you need.
7.Navigate the Parks Smart
Disney parks are meant for their convenience to direct traffic flow, which means a whole lotta walking for you. So find every single shortcut possible! A few easy ones to spot are the walkway through the former Plaza Pavillion to get from Main Street USA to Tommorrowland at the Magic Kingdom. Or there is the way of cutting through the Electric Umbrella to get to the Mission:Space/Test Track Pavillions instead of taking the long way around. Yes they are small shortcuts, but they can save you walking distance, and the hassle of crowds.
8. Be Courteous.
Yes you should do this all the time, no matter where you are but it is especially important at Disney. It's all to easy to find a family struggling to keep everyone alive, and for you to cut them in line or start talking badly about them isn't going to make things worse. If someone asks for help try to help them, if they are a small group let them get in front of you for the rides (note: doesn't apply to groups of loud rambunctious teens I would know, I am one.) Not to mention, it just improves the Disney Spirit in everyone.
9. Know your Ticket!
This might seem common sense but know what ticket you want to buy and what you can do with it. I've helped out people go between parks only to find out they had bought a ticket for one park. I wasted 30mins of mine and their time doing this. Make sure you know where your ticket allows you to travel to. Also spend wisely on your tickets! One park costs about $50 for one day. A park hopper costs even more! Its best to get the multiple day tickets with park hopper since you can come back for however many days you bought, and they don't expire. Or (a little secret here) if you know someone who works full time for Disney, they can pass you in for free! Note this is a free service, if they charge you money it is against company policy, and they may be fired.
10. Have Fun!
After all, why did you spend all that money to come here for? To walk?? I hope not, so make sure you enjoy the moment, and have a good stay. See the fireworks, parades, shows, don't just be fighting to get on a ride.