Buy tickets in advance. If you stay at a Disney resort, you can buy Disney tickets at the hotel and save time when you get to a park. Likewise, you can buy Universal tickets at a Universal hotel. You can also buy tickets online and print them out at home.
Bring a stroller. Even if your child has outgrown his stroller, the stroller is useful for holding bags, drinks, souvenirs and jackets. If your child gets overtired, he can rest in the stroller. You can rent strollers at theme parks, but this adds to the already expensive prices you pay for everything else, so save some money and bring your own.
Wear a bathing suit under your clothes and go on water rides first. Kids usually don't like being in wet suits all day and unless it is extremely hot (the case in July and August) you will stay wet for hours after water rides at all three major theme parks.
Research the theme parks in advance and decide which attractions you want to go to first. Disney World has the FASTPASS and Universal has an Express pass (for those staying at Universal resorts only) allowing quicker access to more popular rides. Try not to disappoint your kids by getting stuck on long lines for the rides they really want to experience. Go there early when lines are likely to be shortest.
Schedule some down time away from the theme parks so kids can have some less crowded and possibly free fun. If you are staying at a hotel with a pool and water slides, you can spend a day enjoying the hotel's free amenities. The Nickelodeon Suites Resort has two water playgrounds and many other kid friendly attractions, all free when you stay at the hotel.
