The Giving Pledge, a project started by Bill Gates and Warren Buffett in which billionaires pledge to give half of their wealth to charitable causes, has a total of 127 signatories after four new pledgers were added last week. These include Kinko's founder Paul Orfalea and his wife, as well as Sheryl Sandberg of Facebook and her husband, SurveyMonkey CEO Dave Goldberg.

Signers of The Giving Pledge provide a statement about their philanthropy, which appears on the website. Among recent signatories, the most illuminating statement by far comes from Craig Silverstein and Mary Obelnicki.

Craig Silverstein. Source: Marcin Winchary.

Mr. Silverstein is often called "Google's first hire" because he joined co-founder Larry Page and Sergey Brin when they were still a start-up, operating out of a rented garage. Silverstein left Google in 2012 but continues to work, as does his wife Mary Obelnicki, who is a software developer. Although the couple are members of the rare few who are both willing and able to give away a half-billion-dollar fortune, their statement reveals approaches to charitable giving that everyone might adopt to become more savvy givers. Here are some of their quotes and how you might use them as a guide to your own philanthropy:

We're not ready to become full-time philanthropists. We like our jobs. We're dedicated to our colleagues. We're raising a family. But we don't want to wait for decades to put our money to good use either. So we simply got started, and we shaped our philanthropy to fit our lifestyle.

Like Silverstein and Obelnicki, you probably have other things you need to do aside from philanthropy. Don't let those completely distract you from being charitable. Find a way for charitable giving to fit into your financial life and calendar, and keep it going once it is started.

We searched hard for one underlying issue where, over time, we might be able to make a difference, where that difference might stick.

What cause are you most passionate about? If you can create a strategic focus (or two) for your giving, you will make more of a difference and gain more satisfaction.

We've been learning along the way: how to find and trust the experts, how to plan not just our philanthropic money but our philanthropic time, and to how support the most impactful, innovative, and promising work possible.

To be skillful at charitable giving takes learning and practice, data gathering and research into nonprofits, and sometimes assistance from a knowledgeable professional. By using your time to be engaged in charitable efforts, you will contribute more and learn more quickly than with financial gifts alone.

Thinking into the future, Silverstein and Obelnicki are expecting to move into philanthropy full-time, saying:

We'll look back and be grateful for the years of learning and giving behind us. We're glad that we've begun now. We'd like to see others join us.

If you put more effort into your own charitable giving now, or continue doing so, you will probably be glad and grateful as well -- even if $500 million in charitable gifts is beyond your reach.