You want to be a good person? Do good things. That voice you're hearing will then tell you that you're only doing these things because you want to be a better person, and not because you're a good person. This is the twisted logic with which we are all too familiar and that offers us a distorted sense of comfort. Yet I can't think of a better reason to do good things than having a desire to become a better person.
Small things at first..."Please." "Thank you." "You're welcome." Hold a door open for someone. Treat yourself to a new tooth brush. (Many of us suck at making major changes; start with the little ones.) Say "good morning" to or smile at a passing stranger. Clean up your room. Do something that's seemingly trivial to improve yourself or your life. Give your seat on the bus or subway to someone who looks like they need a break. Be sympathetic when speaking to someone from "customer support." (Okay, that's a big thing, but you get the idea.) Instead of using a calculator just through an extra buck or two at your server. Perhaps most helpful, Slow Down. A hurried life is often an empty life. Take time to appreciate the value of life itself, the awesome reality of existence, and all the sometimes terrifying, sometimes invigorating possibilities within. Remember, the tortoise won the race.
When we're able to pay attention to life, to our own lives, we discover that there are countless ways to make the world a little bit better.