I found these tips online:
Turn down the temperature, even if you're at the temperature the recipe says. (With macaroni and cheese, food-borne illness is not a huge concern, but for anything that is, use a thermometer to check)
Cover the top with foil for part of the baking. Foil will reflect off a lot of heat, preventing browning/burning. It will also keep humidity inside, so you will probably need to leave loose edges to let it out (if you don't, it may be too soggy).
Move the pan to a different height in the oven. Remember heat rises, and the heating element or burner is on the bottom.
If your macaroni and cheese always burns, add more water or milk to the mix and cook on a lower temperature. Also use foil for half of the baking, then uncover it for the rest of the cooking time.
Good luck with your next batch of macaroni and cheese.