NEW YORK (CNN/Money) - If you're giving money to charity, make sure every dollar counts.

The tsunami that claimed some 155,000 lives as it rocked the coastal areas surrounding the Indian Ocean has already generated donations from tens of thousands of Americans.

Efforts to help people in the region are expected to rank as one of the largest disaster-relief efforts in history. More help is needed, but you should exercise caution in giving. Today's 5 Tips tells you how.

Before you send a check to the first person who solicits your money by phone, stop and think about it. There are nearly a million 501(c)(3) organizations, or non-profit groups, that take tax-exempt contributions. Many of them have similar sounding names but varying degrees of efficiency when it comes to spending your money.

In other words, you will need to do a little work to ensure your hard-earned dollars help the people who need it most.

One of the easiest ways to analyze any charity is to turn to one of the Web sites that provide detailed and comparable information on charitable organizations.

Among the best is Charitynavigator.org, which maintains ratings on individual charities as well as information on how efficiently it spends donations. At Guidestar.org, you can download copies of Internal Revenue Service filings for many nonprofit groups. At InterAction.org, you'll find charities that have met select criteria to become a member.

Unfortunately, it happens that just about every time a major disaster occurs, a scam artist somewhere decides to set up a fake charity to bilk dollars out of well-meaning contributors.

For that reason, don't send money to telephone solicitors you don't know. Watch out for mail solicitations as well. A common scam is to send a request for money disguised as a bill. Appeals that include sweepstakes promotions should disclose that you do not have to contribute to be eligible for any prizes.

If you are contacted by an organization by phone or mail and you want to give to their cause, call the charity directly instead of donating through a third-party. Many states require that solicitors identify themselves as such, and legitimate fund raisers will be happy to send you written information by mail if you request it. You should also ask for written proof that your donation is deductible.

The Red Cross sends letters to all donors regardless of the size of their check, but many charities only provide receipts to those who give $250 or more. So you are better off making your donation by check. That way, you'll have proof of your donation when tax time rolls around.

Also, know the difference between tax exempt and tax deductible. Tax exempt means the organization doesn't have to pay taxes, whereas tax deductible means you can deduct your contribution.

The more you give, the more control you may have over the dollars you donate. Some charities allow donors of $5,000 or more to earmark the money for a specific use.

YOUR E-MAIL ALERTS Follow the news that matters to you. Create your own alert to be notified on topics you're interested in. Or, visit Popular Alerts for suggestions. Manage alerts | What is this?

It's likely that the massive amounts of dollars going to south Asia could strap smaller, domestic charities. You may want to consider writing a check to a local organization at the same time you send money to help tsunami victims.

Local Better Business Bureaus are a good place for information on the performance of small charities.  

Gerri Willis is a personal finance editor for CNN Business News. E-mail comments to 5tips@cnn.com.