Generally, for most recipes, it is best to start on medium heat for thorough heating without burning the outside of the food before the inside is cooked through. When cooking meats on high heat, there can be an assumption that the food is cooked through when both sides of the meat are browned. This is called a sear, which does bring nice flavor to meat. If you have a pan with a handle that is oven safe, try searing chicken breasts, for example, on either side until browned and then finish the cooking in the oven until your food thermometer is 165 or higher. For sauces, such as ground meat with marinara sauce, stick with the medium heat so the sauce is not scorched.