This question is answered IN DETAIL on my 5-set download for your MP3 and also in the book Raise Your Kids without Raising Your Voice. However, here is the short answer: Make sure you give your son loud, clear, even dramatic positive attention when he listens even a little. At these times, tell him that he is “a good listener.” The first few times he listens, give him a reward of some kind as well (i.e. a treat or privilege or a big kiss). This method, which you can learn more about from the resources I mentioned above, is called the CLeaR Method – Comment, Label, Reward.
    When he’s not listening, don’t repeat yourself. Don’t give him loud attention (i.e. don’t yell at him or shout his name). Come to him gently and take him by the hand to draw him to whatever task you want him to do. Remember, he is only 3 years old. Once in a while (definitely not more than once a day!), you can warn him that if he doesn’t do what you asked him to do, you will give him a negative consequence (and tell him what that will be—for example, he might lose his bedtime story or a snack or some other privilege). For instance, let’s say you told him to put his coat on and he just sat there and ignored you. Let’s say that this little guy doesn’t like you to put his coat on for him. You can use that fact for your negative consequence. You could say, “I’m going to count to 5 and if you don’t put your coat on yourself then I’ll have to put it on for you even though you don’t like Mommy to do that.” This method, explained much more fully in the materials cited above, is called The 2X-Rule.
     I do urge you to study more about these techniques. They will help your child listen and become the “good boy” you want him to be!