Since leaving the White House in 2001, Bill Clinton has raised hundreds of millions of dollars for the Clinton Foundation, notably to fund HIV/AIDS care and prevention. His new book, Giving: How Each of Us Can Change the World, urges citizens to get into what he calls the "enjoyable and rewarding" habit of sharing your wealth (or time), no matter how modestly. He talked to PEOPLE's Sharon Cotliar at his office in Harlem.

Why did you write this book?
To tell people that no matter how much time or money you have or don't have, there's something you can give.

How much do you give?
I think the more money you have, the more you should give. I try to give 10 percent to my family's foundation, and then I try to give money over and above that—more or less equivalent to the [high-income] tax cut I get. Because I am opposed to the tax cut I get.

What did your mom, Virginia Kelley, teach you about giving?
My mother was a nurse-anesthetist and her policy was if somebody needed surgery and they didn't have money, you gave it to them. One day in 1961 this fruit picker showed up at the door. He tells me my mother had put him to sleep and had not charged him, but he was a proud man and he paid his debts. He had brought her five bushels of peaches. Well, I thought that was the best deal I ever heard.

How did you teach charity to Chelsea?
I give her mother more credit for that than me. She learned from a very early age that this was just part of living. When she went to Stanford, she did some tutoring and worked at the hospital. She's an interesting woman, my daughter.

What's the best part about campaigning for Hillary?
She worked in every campaign I was in from 1974 when I ran for Congress until I left the White House. So I figure I'm about 20 years behind. I'm doing my best to catch up. I don't play as much golf as I want to, but that's okay.

What keeps you awake at night?
What are we doing to the planet? How are we going to manage inequality? What are we doing to build a better sense of common ground?