Dice all your cheese and vegetables into small, bite sized, bites.
Make the Good Seasons Italian Dressing in a bowl , be sure to double the vinegar, oil and water it calls for on the packet since you are making two. I use a white balsamic vinegar for this dressing to add a layer of flavor. When the dressing is mixed, whisk in the 2 tablespoons of mayo. Set aside.
Cook your pasta until it is al dente. Cook it slightly underdone, because it will be in with the dressing and will continue to soften. So when you're boiling your mini shells, if they taste like they could just use a minute or two, that is the time to take them out, drain them and rinse them in cold water. *side note* YES you rinse pasta when you are using it for a pasta salad. This removes the flour that will make the dressing gloppy and helps the pasta from sticking together in a cold salad.
Add the pasta to a casserole dish, making it in this helps all the dressing and veggies to not sink to the bottom.
Toss in the veggies and the cheese. Toss well so it is really mixed up.
Pour over the dressing. Toss well to coat. Cover and put in fridge minimum 4 hours before serving. Can store in fridge overnight and up to 3 days. Give it a good mix before serving.