Good deeds can be their own reward. They also can reward you at tax time.
When you give cash to a qualified charity, get a note from the group acknowledging your gift if it was $250 or more. If your donation was smaller, you don't need a formal receipt, but you will need some sort of documentation, such as a canceled check or bank or credit card statement, in case the IRS later has any questions.
Are you dropping off clothes and household items at a local collection center? Get a receipt for those. And make sure that the articles were in good shape. The IRS can deny deductions for anything that it deems of "minimal monetary value." In tax speak, that means you can't donate trash and then write it off.
You also can get a tax break for volunteering. You can't deduct the value of your time, but you can deduct 14 cents for each mile you drove to help the group. Documentation of your effort can be as easy as a mileage notation on your calendar on the days you worked.