Use the single rider line on some of the most popular attractions to dramatically decrease wait time.  It is available at Rock N Roller Coaster, Expedition Everest, Test Track, and Mission: Space. 
 

Save money at counter service restaurants throughout the parks by requesting the entree without the sides.  By ordering a sandwich without the fries, you can often save over $2!
 

Save time at the Magic Kingdom by using the Express Stroller Rental.  It is located outside the park entrance.
 

Our family always waits for free dining to come around to book our trip.  But, not only do we take advantage of that, we add on more food and park days than we are actually staying. It only cost a couple more dollars.  Why would we add on more days if we aren’t staying that long???  You can reserve restaurants that take 2 table service meals and you don’t have to pay a lot more for a more expensive meal. Suddenly eating at Cinderella’s Castle doesn’t cost more than a couple dollars!  Thanks to Bryan for this tip!
 

Just wanted to give an update for scoring points on Buzz Lightyear's Space Ranger Spin. In the first room, aim for the left arm of the left robot for 100,000 points, and when you are on Planet Z and you see Zurg, hit the bottom target of his space scooter for 100,000 points. There are some more but I figured I won't give everything away.  Thanks to Dan for this tip!
 

Right next to the Innoventions Plaza fountain is a little know place called Club Cool. They serve unlimited free popular drinks from different countries. A great way to cool down and get out of the crowds!  Thanks to Henry for this tip!
 

This will be my family's 3rd year in a row to go to Disney World.  What most people don't realize is that when you make a reservation, whether it is just for your room or a package, you can make payments at any time toward your reservation.  Every time my husband and I get paid, we call and make a payment toward our Disney vacation. So when we get to Disney, our vacation is already paid for.  Could my family eat a lot cheaper than what I pay for the Dining plan? Sure. But with the dining plan, we get more character breakfasts and more themed dining than what I would pay for when we got there. Not to mention, when I get there, my entire vacation is paid for and I didn't have to charge anything or worry about trying to save the money to pay for it when I arrive.   Thanks to Kim for this tip!
 

My fiancée and I have been to Disney World a total of 5 times since 2000 and it was really just last year that we started to take advantage of the Extra Hours Benefit offered to guests of Walt Disney World Resorts.  What a difference going a bit early or staying a bit late makes in terms of waiting in lines!! First of all, it’s much cooler than in the middle of the day when the sun is its warmest. Second of all, the waits for rides are cut in half!!  There aren’t as many people around at these hours, especially at night, so a normal wait for Splash Mountain might take 2 hours, but at night you might only wait ten minutes.  I understand that staying late might be difficult for families with young children, but if you can manage it, then I highly suggest you do it.  Thanks to Heather G. for this tip!
 

I was eating dinner at the California Grill one night (the restaurant above the Contemporary Hotel). I had just ordered desert when the lights suddenly went off. Then I heard Jiminy Cricket's voice through the speakers.  I realized that they tap the California Grill speakers for Wishes. It is a phenomenal view of the fireworks. It is also nice because you get to see the fireworks and hear the commentary without having to be in a crowd of people.  Thanks to Henry for this tip!
 

I was just reading an article stating to book everything online.....NO! STOP! DO NOT!....get the information/prices resorts etc...., online but call directly. They always have special codes that are not published to the general public and you have to ask for them, if you are staying on WDW property. I found out a month before the Magic Your Way Tickets were upgraded for free to include the park hopper & more just by asking. ALWAYS CALL, either Walt Disney World Travel or your travel agent.  Thanks to Blaine for this tip!
 

Meal plan is awesome. this will be our third trip to Disney utilizing this plan. daily rate is approx $40.00/person/night. so broken down lunch costs around $15/person, dinner w/appetizer, entree, dessert & non-alcoholic drink approx $50/person...Always let the waiter know that you are on the dinning plan when you are seated, some places have unpublished menu items for resort guests on this dining plan, a little more magic offered by Disney.  Thanks to Blaine for this tip!
 

Use Magical Express!!!! Check the Orlando forecast before you leave especially if you are arriving early in the day (prior to 3 p.m checkin), and dress appropriately.  With magical express you do not have to worry about your luggage ...make sure your carry on has what you need weather wise (watch for liquids though thru the airport), and hit the parks after you receive your key to the world, be careful with this if you did not get the park hopper pass though. If you don't want to carry the packet with you to the parks ask them to deliver it to your room. When you arrive in your room your luggage will have magically appeared . . . a fun thing to do is have your kids look for pixie dust.  If they/you don't mind a little glitter you can actually start the magic at home by sprinkling some "pixie dust" in the luggage to make it arrive in your room!!  Thanks to Blaine for this tip!
 

If you are staying on WDW property and this is your first/second and maybe your 3rd time, there is so much to see/do for everyone that renting a car is more than likely not necessary. Their transportation system works very well, however I have not experienced their system during the most crowded times of the season.  We have always gone during low times.  Most time we had to wait was 10/15 mins.  If you would like to see other resorts you will have to take a bus to the closest park and then hop on the "resort" bus that you want to go see.   Thanks to Blaine for this tip!