When Hurricane Sandy devastated parts of the Northeast, people raced to help: They donated money by text and credit card, scoured closets for items to share, and drove to the most ravaged areas to aid in the cleanup. They were motivated by generosity, not tax deductions, and that is how it should be. But the savvier you are about taxes, the further your philanthropic efforts will go.

The write-off for charitable gifts is one of America’s biggest tax breaks — $158 billion in tax year 2009, according to the IRS. Here is a guide to it: