As more images and details of devastation in Haiti make their way around the world, they are being greeted by many with shock, dismay and for some, a desire to help.

For those who are seeking a way to contribute, already there are multiple options, including 800 numbers scrolling across the bottom of television newscasts. The Yele Haiti Foundation, which was founded by musician Wyclef Jean, has become a huge focus on Twitter and lets people donate by texting a specific number. And no less a figure than President Obama, who has promised U.S. support to Haiti, is encouraging Americans to help by donating money. But rather than giving on impulse, it s important to maximize the impact of your contribution, especially with so many groups vying for your dollars amid the chaos, experts say.

Con artists will strike when emotion is high and the news is new, says Bennett Weiner, the chief operating officer for the Better Business Bureaus Wise Giving Alliance, which reviews charitable groups.

In the case of Haiti, there are some significant challenges to any relief efforts. Much of the country s infrastructure remains damaged by four severe floods that struck the country in 2008. The money that came in was spent as wisely as it could on medical supplies and some infrastructure repair, slapping up makeshift buildings to put patients in, says Amy Wilentz, a noted commentator on the nation and the author of The Rainy Season: Haiti Since Duvalier. The bigger thing is rebuilding, and that s a matter for foreign aid rather than from people like you and me.

After the 2008 floods, CHF International, which offers aid to low-income communities, was able to provide assistance in Haiti within two to three days. But those floods were more localized, says David Humphries, a spokesman for CHF. It will take longer to get aid following the earthquake, which left more widespread devastation. He estimates aid this time around may be delayed by as many as three to four days.

Here are some guidelines that philanthropic experts suggest for giving to Haiti now.

1) Stick with established groups

Don t offer your cash to the first telemarketer or to people tabling for donations on the street. Even a legitimate but newly formed group isn t a great choice. Though the group may have good intentions, it is unlikely to have the connections and processes that established charities do to get your money where it is most needed, says Weiner of the Wise Giving Alliance.

Instead, search for a group through independent charity evaluators including the Wise Giving Alliance, GuideStar and Charity Navigator, which all assess the efficiency of registered public charities recognized by the IRS.

2) Assess the charity s plan

In times of crisis, a lot of people want to do something, says Bob Ottenhoff, the chief executive for GuideStar. But this is a time where we need the experts. Your best bet is a charity that already works in Haiti -- there are more than 700, he says. (These groups are more likely to be there to aid long-term recovery efforts after immediate ones.) Read descriptions of a group s programs, and look for specific numbers (houses built, meals distributed) that point to its success. Groups equipped to help smaller clinics now that larger hospitals have crumbled, include Doctors Without Borders, the Red Cross and local groups, such as Zanmi Lasnate (Partners in Health, a clinic run by Dr. Paul Farmer of Harvard University, says Wilentz.

In the case of the current crisis, the immediate concerns are the breakout of epidemics from bad water, a lack of food, rampant injuries and a lack of medicines, says Kathleen Balutansky, who was born and raised in Haiti and is the associate dean for academic affairs at St. Michael s College, a liberal arts school in Colchester, Vt.

For more tips on assessing a charity s effectiveness, click here

3) Designate your gift

Normally, it s best to make a general donation to the charity and let them decide how to use it. But if the charity has several programs and you re sure you want your donation to go to earthquake relief, note that preference on your mailed check or in the special instructions box for online donations.

4) Write a check and don t use plastic

The earthquake survivors do need clothing, food and potable water. But the cost to transport such goods is considerable, says Ottenhoff. It s more effective to send cash, which the charity can use to purchase goods and services locally.

American Express and Visa announced Thursday that they would waive interchange fees through February on donations made to approved charities supporting Haiti relief efforts.) Fundraising site NetworkforGood.org takes a 4.75% cut of donations paid though PayPal or a credit card.

5) Watch out for phishing scams

If you re donating online, be thorough. Once you ve decided to give to, say, the Red Cross, link to the site directly from that of a charity evaluator to make sure you have the right site. Look-alike phishing sites aiming to steal your financial information are another common post-disaster scam, says Weiner.

UPDATE, Jan. 15: Card issuers including American Express and Visa announced Thursday that they would waive interchange fees through February on donations made to approved charities supporting Haiti relief efforts.