We just returned from our first ever trip, and we used the dining plan. It was great. My advice is as follows:
1) Make ADRs for your TS meals!! If we hadn't made ADRs, I'm not even sure we would have been able to use our TS meal credits. Everywhere we went, we saw walk-ups being turned away due to no availability.
2) Download the CS menus from this site and decide where you want to eat at each of the parks.
3) I wouldn't bother with trying to share meals. We are a healthy (not-overweight) family of 4, and after all that walking around, 1 CS and 1 TS per person per day (plus an OOP breakfast) was NOT too much food. It was just right. I suggest you each just get your own meal. That way, you don't have to calculate how many you have left and whether you're leaving any unused.
4) Go ahead and get the snack you want when you want it. After looking at the list of allowable snacks, I didn't want to "waste" any snack credits on a measly ice cream bar or popcorn, I wanted to save them for the really good stuff.... so we ended up with 11 snack credits to burn on our last day!!! It would have been better to let the kids get the $2.00 ice cream and enjoy at the park, rather than load up on $3.95 boxes of cookies to give to people when we got home.
5) If you each want to try a different country's CS in Epcot, just ask for your orders to go. They'll pack your meal in a styrofoam container so you can meet back up. We each had our favorite cuisine at one of the tables near Oris Orisi.
Those are what worked for us, and what we might do different next time.