When a supposedly noble cause pulls at your heartstrings, don't be too quick to loosen your purse strings.

By following these how-to steps below, you can avoid the scams and get the most benefit from every charitable contribution.

With more than 500,000 organizations competing for your charitable dollar, it’s difficult to separate the altruists from the con artists.

The large, household-name charities tend to be the safest bets. But thousands of new charities are created every year, and a growing number of them are either marginal or downright crooked. The rise of 'charitable' solicitations over phony web sites has only spawned more innovative ways for unethical sharpies to exploit your emotions and tap your wallet.

Here are three tips to ensure that you maximize the benefits of your charitable donations.

#1: Know the Most Common Scams

To avoid getting ripped off, watch out for charities that:

Predicate their pitch on a timely natural or man-made disaster. Misfortune tends to bring out the fortune hunters. Even the terrorist attacks of 9/11 were cynically exploited by fake charities.

Send 'spam' seeking charitable contributions. If it’s an unsolicited email message asking for a charitable donation, chances are it’s fraudulent.

Send e-mail from a person pretending to be from an institution that you use. They ask for highly personal information such as your Social Security number or tell you to click a link. This scam is known as 'phishing.'

Exert high-pressure sales tactics. For example, some 'charities' call and offer to send a messenger to your house to pick up your donation. This is an increasingly common scam. Most honest charities are willing to wait to receive your donation in the mail or over a secure web site.

Refuse to provide financial statements or annual reports.

Disguise their appeal as a bill or invoice, a practice that’s illegal. This sort of solicitation is typically geared to the elderly, so it’s prevalent in the Sun Belt and other areas with large numbers of retirees.

Offer a high-cost 'affinity' credit card, where a portion of each purchase goes to the charity that’s sponsoring the card. It’s an easy way to give, but these cards’ interest rates and fees usually are higher than those of conventional credit cards. Moreover, these contributions aren’t tax deductible. Ask the charity the size of its cut of the annual fee and the interest rate you pay on the account, to make sure that the bank isn’t siphoning away too much of your money. On average, the sponsoring charity’s portion is 0.5 percent.

#2: Ensure That the Charity Uses Your Donation for Charity

The three major and legitimate expenses incurred by charities are fundraising, management/administration, and program services (the reason money is raised). According to watchdog groups, a charity should devote at least 50 percent of its total income to program services. Most reputable groups spend about 75 percent. No more than 35 percent of money brought through fund-raising should be spent on the fund-raising itself.

This information is readily available from several places, including the charity’s annual audited financial statements and the IRS Form 990, the annual tax return that charities are required to file. The form is available from either the IRS or the charity itself.

Non-profit, tax-exempt charities must file and post their tax statements for public inspection if the charity receives over $25,000 per year. These tax filings must include information about their income and how it was spent, including how much their officers are paid. To find this information, go to the charity-funded public watchdog site GuideStar.

Be aware of the semantic games that some charities play. For example, the cost of direct-mail fund-raising is sometimes described in the annual report as 'public education' expenses. But also realize that new charities may have higher fund-raising overhead than established charities with wider donor lists.

#3: Plan Ahead to Maximize Tax Deductions

Once you’re found a charity that appeals to you and meets the above standards, figure out what’s tax deductible.

Ask the charity for its 'letter of determination,' the formal notification an organization receives from the IRS once its tax-exempt status has been approved. This letter can tell you what is and isn’t deductible. Or contact your local IRS office. A donation to any organization that’s been granted '501(c) (3)' status by the IRS is tax-deductible.

Most charities are tax-exempt organizations that don’t pay income taxes. But many people don’t realize that contributions to tax-exempts, such as fraternal orders, aren’t automatically tax-deductible.

Remember: Good deeds aren’t necessarily good deductions. For example, it’s a common mistake to think that the value of blood given to a blood bank is deductible -- it isn’t. Donations to needy individuals aren’t deductible, either. Pledges aren’t deductible until the year in which they’re actually paid.

You don’t have to itemize contributions under $500 but be prepared to support in case of an audit. To get a deduction, you must have made the donation on or before December 31st of that tax year.

Your tax deduction for non-cash property gifts (stocks, real estate, etc.) is the fair market value at the time of the gift. That means you don’t have to pay taxes on any appreciation that occurred while you owned the asset.

In any one year, you can deduct no more that 50 percent of your adjusted gross income in charitable contributions. For appreciated property, the amount you can deduct is 30 percent.

The fair market value of goods donated to a thrift store is deductible as long as the store is operated as a charity. To determine value, visit various thrift stores and check the 'going rate' for comparable items.

If you receive goods or services (such as a prize) in return for your contribution, only the amount of your donation exceeding the value of what you receive is deductible.

The purchase price of tickets to a fund raising dinner, circus, or other meal or entertainment event is not fully deductible. Only the portion of the ticket price above the value of the meal or entertainment can be deducted for income tax purposes. As proof of a cash contribution, all you need is a canceled check.

However, it’s advisable to keep receipts as well as cancelled checks for all donations. For non-cash property gifts in excess of $500, you must file IRS Form 8283. For non-cash property worth more than $500, you’ll need a written appraisal from a professional appraiser.

The Investing Answer: The fact is, some charitable solicitations are more greedy than needy. By following this common sense advice, you can avoid falling pray to a less-than-sweet charity.