Because slow cooker models vary, make sure you read the manufacturer's instructions before using yours for the first time. Some slow cookers need to be preheated before you start cooking; others advise against heating it when empty.
Before using for the first time, wash the inner ceramic cooking pot in hot soapy water, rinse and dry. You may notice a slight odour as the slow cooker heats up; this is caused by the burning off of manufacturing residues and should disappear after the first few uses. Don't worry if the ceramic glaze becomes slightly crazed; this is perfectly normal.
You'll notice that many of the recipes advise using very hot, not boiling, water and stock when adding it straight to the cooking pot. Never pour boiling water into the cold cooking pot (you can do so when it is already warm or hot, or when there are other ingredients covering the base) nor plunge it into cold water immediately after use as this could crack it. Remember that it is an electrical appliance, so the outer casing should be wiped clean and never immersed in or filled with water.
When following a recipe, bear in mind that every model is slightly different and, even when using the same settings, some will cook much faster than others. For this reason a range of cooking times is given on most recipes; check after the shorter time given, this will usually be sufficient, but the food won't spoil for the extra time. Some small models cook quite quickly on High, so you may prefer to use the Low setting. After trying a few recipes, you will know whether your slow cooker is faster or slower and be able to adjust the recipe cooking times accordingly.