If you receive a no to any of these questions it is best to stop and try again later. Your frame of mind and emotional state is important to your ability to dowse effectively. To avoid the possibility of auto suggestion you may want to close your eyes when starting an experiment. Try testing foods. Be careful to place food in a clean neutral place.
Many people dowse for optimum health, good foods, vitamins etc.
Be very clear and literal in your wording as a single word can change the meaning. Hold the question firmly in your mind. Writing down both the questions and then the answer can be helpful. Get the full answer to the first question before you go on to the next question. It is a good idea to halt your pendulum before continuing.