Beware of organizations that use meaningless terms to suggest they are tax exempt charities. For example, the fact that an organization has a “tax I.D. number” doesn’t mean it is a charity; every nonprofit and for-profit organization must have a tax I.D. number. And an invoice that tells you to “keep this receipt for your records” doesn’t mean that your donation is tax deductible or that the organization is tax exempt.

• Be skeptical if someone thanks you for a pledge you don’t remember making. If you have any doubts about whether you’ve made a pledge or previously contributed, check your records. Be on the alert for invoices claiming you’ve made a pledge. Some unscrupulous solicitors use this approach to get your money.
• Ask how your donation will be distributed. How much will go to the program you want to support (as opposed to other programs of the nonprofit), and how much will cover the charity’s administrative and telemarketing costs?
• Refuse high pressure appeals. Legitimate fund-raisers won’t push you to give on the spot.
• Be wary of charities offering to send a courier or overnight delivery service to collect your donation immediately.
• Consider the costs. When buying merchandise or tickets for special events, or when receiving “free” goods in exchange for giving, remember that these items cost money and generally are paid for out of your contribution. Although this can be an effective fund-raising tool, less money may be available for the charity.
• Be wary of guaranteed sweepstakes winnings in exchange for a contribution. According to law, you never have to donate anything to be eligible to win.
• Avoid cash gifts. Cash can be lost or stolen. For security and tax record purposes, it’s best to pay by check.Source: Federal Trade Commission