You need a type of fat and some flavoring. Design your own. Use olive oil, sesame oil or melted butter. Regular salt, seasoning salt, fresh herbs, dried herbs, fresh garlic, garlic salt, liquid smoked, soy sauce, etc. Get any combination--to the max or simple. A plain bread-and-butter crouton is a delight in a delicate salad. A soy-and�sesame-oil crouton works in a Napa cabbage Asian salad.
Use any bread that is stale before it molds. Once the croutons are cooked, they keep in an airtight container for weeks.