(Money Magazine) -- Recently I had coffee with a friend who was venting. This was normal - what are friends and grande skim lattes for?

What was out of the ordinary was the topic of that day's rant: charitable giving.

It seems that her husband had discouraged her from writing a check to a child-care foundation that was important to her, only to turn around and write one to a cancer group himself. Her beef was not with the donation (his sibling had recently been diagnosed with cancer, and the charity was topnotch) but with the predicament that such spontaneous giving could land them in.

She wondered aloud, "Wouldn't it be better to sit down and decide how much we're going to give and to whom?"

She took the words right out of my mouth. Ask most people why they give, and they'll tell you someone from a worthy cause solicited them. "People give in response to being asked to give," says Eugene Tempel, executive director of the Center on Philanthropy at Indiana University. However, since Sept. 11 (after which $1.88 billion was raised through public appeal), the tsunami ($2 billion) and Hurricane Katrina ($3 billion), some kinds of giving have become more reflexive than ever.

Even if you're making a Warren Buffett-style $37 billion gift, too much spontaneous check writing, no matter how well-intentioned, doesn't help anyone much.

Knee-jerk donations aren't just bad for your own finances; in many cases they don't benefit the recipients either. In his new book, "The White Man's Burden," New York University economics professor and former World Bank researcher William Easterly points out the pitfalls of windfall gifts, such as the potential for aid groups to become so overwhelmed with donations that they can't spend the money fast enough.

A report released in June by the American Red Cross acknowledges the challenges it faced responding to Hurricane Katrina, including tracking supplies, detecting duplicate financial-assistance payments, distinguishing actual victims from fraudsters and handling the overwhelming number of online donations.

What's the solution? It's certainly not simply to ignore hurricane victims. Trent Stamp, president of CharityNavigator.org, which rates more than 5,000 charities, suggests starting with an 80-20 split. Earmark 80% of your annual giving for a specific mission while reserving the other 20% for spontaneous donations. Then follow these suggestions.

With a little Googling, it isn't hard to identify a charity that addresses a big problem like homelessness or AIDS. But if you're looking for something local or more specialized (a neighborhood school that needs books, for example, or the most reputable programs that work with the elderly), ask a community group for guidance.

Someone who has deep roots in your community, such as the head of your local YMCA or Rotary Club, might know of individuals and groups that could use your help, and may be able to match you with a cause you feel good about. The benefits are twofold: When you give to a small charity with less bureaucracy, your money can make more of a difference.

Also, instead of joining the millions of people who give to, say, the United Way, you'll get the satisfaction of having discovered a cause closely aligned with your goals. "We take this responsibility very seriously," says Alan Trager, CEO of Westchester Jewish Community Services in Westchester County, N.Y. "Spending other people's money is a much more serious enterprise than spending our own."

Bet you never thought you'd hear that advice in Money Magazine. In fact, says Stamp, while it's okay to pick a few pet causes, you shouldn't diversify your giving as you would your portfolio.

Organizations spend a lot of money to cultivate you as a donor. If you give only a few dollars here and there, most of your money could get swallowed up in administrative and fund-raising costs. Give as much as you can to fewer causes, however, and they can allocate more of your donation to the mission.

The other downside to being a small donor? Your name in the database is worth more than the gift itself. That's why some charities, once they see that you give only $20 or $25 a year, will sell your name rather than continuing to solicit you themselves. All of a sudden you've got a mailbox stuffed with pitches.

A good rule of thumb is that at least 70% of your donation should go toward supporting the underlying mission rather than to administrative costs. Before you write a check, vet the organization using Charity Navigator (charitynavigator.org) or the Better Business Bureau Wise Giving Alliance (give.org). You want to make sure your donation is put to good use, and charities know that.

That's why these days, so many employ what is known, for better or worse, as the Sally Struthers pitch, whereby you're told exactly what, in theory, your gift accomplishes. When you make a donation through the Habitat for Humanity website, for example, you are informed that $10 buys a box of nails, $50 a low-flow toilet and so on.

Use that to help you determine how much you want to give to a group; then hold them to their promise by requesting a copy of their annual report, which should give you an even better idea of what can typically be accomplished with the amount you gave.

Ah, the ultimate question. The average American household donates 2.2% of its income each year, or roughly $1,000. Churches ask that people who tithe give nearly five times that; other, secular organizations use 5% as the target.

How deep you should dig, of course, depends on your other obligations. For the same reason that it's easier to pay off credit cards by putting aside a set amount each week, I find it much less daunting to think about how much I want to give in terms of dollars per paycheck rather than an annual percentage.

Some large groups even offer an automatic deduction. This is smart because, Stamp notes, the fact that you can't give as much as Buffett is no reason to give haphazardly.

"Don't use that as an excuse to say 'I don't have to be as strategic,'" he says. "Instead, say 'I have only a little to give, so I have to be even smarter.'"