When handling raw chicken, you must keep everything that comes in contact with it clean. Raw chicken must be rinsed and patted dry with paper towels before cooking; cutting boards and knives must be washed in hot sudsy water after using and hands must be scrubbed thoroughly before and after handling.
Why?
Raw chicken can harbor harmful salmonella bacteria. If bacteria are transferred to work surfaces, utensils or hands, they could contaminate other foods as well as the cooked chicken and cause food poisoning. With careful handling and proper cooking, this is easily prevented.
Chicken should always be cooked completely before eating. You should never cook chicken partially, and then store it to be finished later, since this promotes bacterial growth as well.