Hello, Amanda!
I love this question!
To maximize your dining $ on a Disney Dining Plan, look for items which are a splurge. For example, Wolfgang Puck's Express, at Downtown Disney, offers a really spectacular menu as a Quick-Service! For a menu, head to the unofficial website allears.net, where you'll see offerings at breakfast, lunch and dinner which will make you think that you are reading the menu of a Table-Service location. Yum!
When sitting down to a Table-Service location, look for items you would not splurge on should you be paying cash, but would really love to try (i.e.
Le Cellier, in Epcot's Canada, still counts as 1 Table-Service credit for LUNCH, but they offer the very delicious Wild Mushroom Filet Mignon, for 27.99, on their lunch menu. While I'm sure I'd love the Le Cellier House Burger, I'd rather relish the Filet, if I can order either one on the DP. Also, check the menu for Sunshine Seasons, a Quick-Service at Epcot, for some fabulous options with really lovely desserts!)
For snacks, look at posted menus, which include the DDP sticker next to any item which counts as a snack. Order what is the best value. A waffle cone or a funnel cake, a Dole Whip or a stash of crispy fries with cheese sauce, an iced latte or a cream cheese-stuffed soft pretzel can all be obtained through a snack credit. Look for items to indulge in which cost more than a bottle of water.
When you have "leftover" snack credits, head over to Goofy's Candy Co. at Downtown Disney, where you can pick up giant turtles (chocolate, caramel and nuts) or customized chocolate-covered pretzel logs, great souvenirs to take home from your trip, as well!
Send more questions with your favorites and I'll let you know where to find them as a snack! :-)