Training - Teach your Mastiff to walk nicely on a leash

Begin obedience training by teaching your Mastiff to walk nicely on a leash. Let him walk ahead of you a bit on the long lead. As he begins to pull, pop the leash firmly (using the slip chain collar) to get his attention. Say the word "Easy" loudly and firmly, then change your direction. The idea is to get him to stop, look at you and then change direction with you.

Be sure to praise him when he does this. This command also works in teaching him to walk slowly alongside you without pulling. Just use the same technique, but without changing your direction. It is important not to tug or haul him around with that leash. He should be learning to follow you with a very loose lead. Pulling will only cause more problems. The "Easy" command can also be used as a correction if he is acting aggressive towards a person or another animal. Be sure you keep your voice strong.

Mastiff - Dog Lover

DOG FAQ - Does the Mastiff Shy?

Because of their great sensitivity, Mastiffs who are not throughly socialized when young can very easily become shy of strange people, places, and animals.
Shyness can be both inherited and/or the result of inadequate socialization. This is why puppy kindergarten, obedience classes over an extended period of time,
and visits to parks are extremely important to the development of your Mastiff. If you do not have the time to do these things with and for your Mastiff, you need to think over whether you are in a position to do right by a dog, at least at this point in your life.

A shy dog is an uneasy, unhappy dog. If your dog is more shy than the average, then it is more important than ever to get the right amount of gentle, gradual socialization with lots of positive reinforcement for all its friendly, confident, non-shy actions.

Mastiff - Dog Lover