There is no one definitive answer to this question as everyone may have their own opinion or method on how to train a dog to sniff out bed bugs. However, some tips on how to train your dog to sniff out bed bugs may include using positive reinforcement methods such as treats or praise when your dog correctly identifies the presence of bed bugs. You may also want to create a mock infestation in your home by hiding bed bugs in different locations and having your dog search for them. As your dog becomes more adept at finding bed bugs, you can increase the difficulty of the searches by hiding the bed bugs in harder to find places. Ultimately, the goal is to have your dog be able to indicate the presence of bed bugs by sitting or lying down next to the area where they are located.