Hello, Jennifer!
The advice you received regarding booking your dining reservations in advance was excellent!
With the popularity of the Dining Plans, so many folks are booking Table-Service reservations that it often becomes next-to-impossible to get a reservation once you get into the park. To be sure that you book those advance dining reservations at locations where you'll want to be each day,
take a look at Park Hours and Updates, which can be found on Walt Disney World's main page. (Scroll to the bottom of the home page, and, on the left side, under "Parks," you'll see "Park Hours." Click that and it will take you to a spot where you can select the first date of your trip.)
Then, once you've mapped out which days you'd like to be in each park, take a look at your dining options in each location. Don't forget to include your dining options at resorts as well as at Downtown Disney, too. (Dining at Chef Mickey's or Ohana, for example, is very easy when you're spending the day at Magic Kingdom Park.)
Please send any additional questions as you think of them; I'd love to help! Happy planning!