Each dog has its own distinct personality, and each personality is unique. This personality depends on a lot of things like genetics, circumstances and self-development characteristics. This is what makes some dogs assertive and some mild and timid.
Dogs that are assertive or aggressive to an extent are always trying to be the alpha male. They are the ones who are always trying to take toys and bones from others, enter first, and are more demanding. Dogs that are timid are those that eat last, enter last and will never want to be noticed.
When you first notice a timid dog, you usually think that it is a well-behaved dog and one that does not need any training. This is because we perceive training as discipline, where we are always curbing the animal from some particular form of behavior. An assertive dog is punished and disciplined when he is not obeying his master and he usually pulls the leash while walking or during exercise. Assertive dogs are trained to not chase every stray dog or cat. Fetch and catch is a game that is played with them for training. Comparatively timid dogs will wait quite patiently for everyone to leave and then exit, they do not dig, chase animals or show any form of indiscipline. You will notice a timid dog standing apart from the other dogs in the house. This should be your first sign that a dog is timid in nature.
Not all-timid behavior is welcome. Sometimes timid behavior can be harmful to the dog and the family. People keep dogs as a security measure, to bark at strangers and protect the home they live in, but if the dog is too timid then he will allow any stranger to approach him. This is harmful to the dog especially if the dog accepts treats and food from strangers, which could hamper the set diet and could even be fatal. Training a timid dog requires teaching him boundaries. These boundaries need to be respected by the dog and by unfamiliar humans. This means training a timid dog in a manner where he becomes aggressive when his personal boundary is crossed by an unfamiliar person. Treats and food should be discouraged, especially when given by unknown people.
The trick to training a timid dog is to work with his nature or personality and not against it. This means if the dog is not aggressive, do not force it to be. All dogs, especially timid dogs love playing fetch and love being rewarded. Reward your dog for a task well done. Remember that just because your dog is timid does not mean it is scared. If you have more than one dog, then you need to take the most timid dog for a walk alone. In this way, there is only one alpha male and that is you. At these times you should encourage your dog to enter the house first, to eat first and do other things first. This gives the dog a sense of confidence and will help it become less timid and docile.