This is how I make meatloaf....
1 pound ground beef
about 15 crushed saltine crackers
1/2 medium bell pepper, chopped
1/2 medium onion, chopped
1 stalk celery, chopped
1 tsp salt
1 tsp black pepper
1/4 cup prepared yellow mustard
1/4 cup ketchup
Mix these all together real well and put in a baking dish (9x11x2") - form a mound or a loaf shape in center of dish; this leaves room for the fat to cook off.
Mix together another 2 Tbls. of prepared mustard and 2 Tbls. ketchup and spread over the top of the meatloaf before baking at 375*F for 45-55 minutes.
To double just double everything. You may even spice it up a bit by adding other spices and herbs - basil, parsley, Italian seasoning, etc...