Drain the wettest ingredients during the preparation. That way you don't end up with a super soggy casserole.
Pre-heat your oven before popping the casserole dish in there. This ensure that your cooking time does not become an extended version of "Is it ready yet?"
Spray the bottom of your casserole dish first with a cooking spray or light brush of oil to prevent sticking. It also helps crust the bottom a bit, for some, that is the best part!
Use the right size casserole dish for the job. A 9x9 or a 9x13 dish with at least 2 inch depth is ideal. However, you can also use a cast iron pan if you prefer.