Teaching your dog to say no can be fun for you both. You can ask her questions you know the answer to in front of friends and have her reply with the answer "no". Not only can this be fun and entertaining for your guests but training with your dog is also rewarding for you. Teaching your dog to say no is another way for the two of you to bond. Your dog is going to love the treats he receives and the attention he gets from you when he does something right. And you will have a dog who knows a cool and relatively simple trick. If you can also get your dog to understand the reason for communicating "no" to you, your dog will be able to make complex independent decisions.
Teaching your dog to 'say no' itself can be quite simple. It is a repetitive command that you practice with your dog over and over until he understands the motions of no and the reaction to saying "no". Teaching your dog to comprehend the word "no" and when he should say "no" to you becomes a little more complicated and will take more time. Teaching your dog how to communicate "no" can be a fun trick, and it can also be a major task if you have a service dog you are trying to train to help others.
You will need a couple of pieces of paper and a couple of chairs to teach your dog the motions of saying no. Be sure to stock up on some special obedience training treats so your dog is rewarded when he gets it right. If you use a clicker to click train your dog, you may want to use a clicker here as well since your dog is used to the click and treat reward method. Be prepared for short training sessions that are repetitive and plan to visit with your dog often to work on communicating "no".