The cooking temperatures and settings vary on different models, but most have four settings: Low, High, Auto and Off. Some models have an additional Medium setting. At the lowest temperature the food should barely simmer: at the highest it will boil very gently.
Use the Low setting when you want to cook food for an extended time without overcooking or burning.
When set to Auto, the cooking temperature will build up to High (the time this takes depends on the quantity of food being cooked and its initial temperature), then remain at this temperature for an hour or so before automatically switching to Low.This setting is desirable if you are using frozen vegetables in your cooking without defrosting them first. Foods such as poultry joints (chicken quarters and whole thighs, for example, but not breasts or chopped chicken) and cakes should be always be cooked on High or Auto. Food should be monitored when using the High setting as some liquid will evaporate.
Some flexibility can be introduced to the total cooking time by adjusting the temperature settings; for dishes such as soups, braises and casseroles, the cooking can be shortened or extended to suit your needs by changing the temperature setting. As a rough guide, the cooking time on Low is about double that of High.
If at the end of the cooking time the food is not quite ready, replace the lid and switch the setting to High to speed up the cooking process. Once ready, many dishes, especially casseroles and soups, can be kept hot for an hour or more without any risk of spoiling by switching the temperature to Low.
If you are planning to go out for the day and your chosen recipe does not take as many hours to cook as you will be away, you can use a time-delay plug so that the start of cooking is delayed by several hours. This is particularly useful if you are including a large quantity of frozen vegetables, which will then have a chance to thaw during this time and come up to room temperature before cooking starts. It's important that all the ingredients - including stock - are cold (preferably chilled) when added to the ceramic cooking pot. However, never use a time-delay plug when cooking chicken or when the kitchen will be warm, for instance on a sunny day, or if the central heating will be on before cooking commences.
Modern slow cookers tend to cook at a slightly higher temperature than those that are 10 or more years old so, if you have a newer model, check whether the food is ready at the minimum suggested cooking time when following the first few recipes.