Make sure you don’t add the cheese at the beginning. Allow the casserole to bake up and then add the cheese towards the end of the baking process.
Crush the Doritos a bit in the bag to create less mess.
Store in an airtight container and refrigerate for up to 4 days. After that, it may be a bit too soggy.
I don’t really suggest freezing this since the texture doesn’t quite remain the same.