Fill cooker no less than half full and no more than two-thirds full. Vegetables cook slower than meat in a slow cooker, so if using them, put vegetables in first, at the bottom and around the sides of the pot. Then add meat and cover the food with liquid such as broth, water or barbecue sauce. Keep the lid in place, removing only to stir the food or check for doneness. Most cookers have two or more settings.
Foods take different times to cook, depending upon the setting used.
Certainly, foods will cook faster on high than on low. If possible, turn the cooker on the highest setting for the first hour of cooking time and then to low or the setting called for in your recipe. While food is cooking and once it's done, it will stay as safe as long as the cooker is operating. When you are at home, and if the food was completely cooked before the power went out, the food should remain safe for up to two hours in the cooker. The same is true if you forget to turn on the cooker after putting in the ingredients.