Ask and ye shall receive, Dallas deejay Ron Chapman figured. But he didn't expect to get too much when he told his listeners on March 31, 1988, to "go to your checkbooks. Write a check payable to KVIL Fun and Games. Make it in the amount of $20 and mail it to this address."

He offered no promises and gave no explanations, but within a month there were 12,212 checks worth almost $250,000. KVIL ended up donating the money to civic projects and charities, which is presumably what all those listeners thought they were giving to in the first place.

It's incidents like these that reinforce the notion that Americans are not only generous givers but often rather impulsive about it. Okay, call them occasionally foolish. Someone phones with a story about needy children or disaster relief or a breakthrough in cancer research, identifies his organization and makes the cause sound legitimate, and the check is in the mail. In a 1988 Roper survey, almost a third of respondents admitted they had donated without understanding precisely what the recipient did.

There's a flip side to such kindly behavior. That's those cynical souls who don't give anybody much of anything, on the presumption that the majority of their dollars are going to end up paying the fundraisers or administrative costs, so why bother?

In a series of focus groups conducted in August by the Public Agenda Foundation, nearly all the respondents said they felt most charities "waste" a fair amount of money: about a quarter out of every dollar donated, they believe. And 77 percent of the Roper respondents agreed it was difficult to know which organizations were legitimate.

Two new handbooks and a recent issue of a little-known magazine can help consumers make sensible choices. All of them stress that a donation to charity -- particularly a larger sum, $50 or $100 or up -- shouldn't be thought of as merely an end-of-the-year ritual or an opportunity for a tax deduction.

"You should give your contribution as much consideration as any important investment," says Howard Gershen, author of "A Guide for Giving." "Because it is an investment -- in the future of the world, in curing a disease, in housing the homeless or helping people gain civil and human rights."

A bit of preliminary investigation will not only weed out the more obvious scams, but can offer a better match-up with your particular interests. An example offered by Philip English Mackey, author of "The Giver's Guide": "Most people think, 'If it's got 'animal' in the title, that's enough for me, I'll give them some money,' " he says. "It shouldn't be that simple."

The Fund for Animals, for example, uses 47 percent of its budget for animal rescue and protection, while Friends of Animals devotes 73 percent to spaying cats and dogs. The National Wildlife Federation, meanwhile, is basically geared toward educational material. "I'm not saying one is better than another," says Mackey, "but one of those things probably grabs you more."

The write-ups in both "The Giver's Guide" and "A Guide for Giving" tend to be straightforward, letting the numbers speak for themselves. The latter, published by Pantheon, covers 250 charities, from the Account for POWS/MIAs Inc. to Zero Population Growth. Tax-deductibility, purpose, size, income and related topics are covered, including ratings from the National Charities Information Bureau (NCIB).

A pie-chart for each charity divides the money spent on program, fund-raising, overhead and "excess." The most important figure to remember is 60 percent, which is the NCIB standard for the slice of annual expenses that should be devoted to program -- the charity's reason for existing in the first place. This is a minimum, but charities don't always meet it.

The National Emergency Medicine Association, for instance, is presented as having spent 57.6 percent of its 1988 income on fund-raising. The New York-based drug-abuse treatment center Phoenix House Foundation is described as having spent 42.9 percent of its fiscal '88 income on overhead. Sometimes, as the National Emergency Medicine Association contends in its case, such figures are one-time aberrations; but if you care about what happens to your donation, it never hurts to ask.

The first 50 pages in "A Guide for Giving" are devoted to an overview of the charity field, including such new developments as affinity cards (where a small amount goes to a charity every time you use a specific charge card) and cause marketing (most prominent of which are rock concerts aimed at alleviating one crisis or another).

This is interesting stuff, but much less directly practical than "The Giver's Guide" (Catbird Press, 44 North Sixth Ave., Highland Park, N.J. 08904). Mackey spends his first 80 pages covering very basic territory in Q&A format. In an interview, he sums up: "What you should be doing is shopping.

"Figure out an area that concerns you, and find information about eight or 10 charities that work in the area. Then compare the figures on how much of their dollar is going into their programs. In virtually every case, you can make some wise decisions.

"This is the opposite of what most people do now, which is give to a charity by waiting for someone to come along -- either literally to their door, or by telephoning them or through the mail. That's like shopping for appliances by waiting for someone to come along."

The bulk of "The Giver's Guide" treats 300 national charities in somewhat the same format as Gershen's effort. Mackey relies on the National Charities Information Bureau data and critiques, while Gershen uses information directly from the charities' IRS reports.

Gershen claims, therefore, that his competition is relying on secondhand information. Mackey's publisher, meanwhile, notes that "charities tend to make the best case for themselves, and therefore their information needs to be filtered through a critical accounting such as the one offered by the NCIB."

One feature of Mackey's guide is a listing of each charity's top salaries. "It's another element in comparison shopping," says the author. "At the International Rescue Committee the top salary possible is $60,300, while at Project Hope it's $195,000. Maybe there's a justification, but if you're trying to shop between them, call Project Hope and ask why. After all, their budgets are fairly similar."

How do you get information on what a national charity does with your money? The first step is asking -- not only for a colorful brochure, but some financial data, too. Ask for an audited annual report.

An independent source of evaluations can be had from NCIB's "Wise Giving Guide" (Write 19 Union Square West, New York, N.Y. 10003, or call 212-929-6300). This is a free pamphlet that lists more than 300 national charities and rates them according to a variety of standards. More detailed information can also be found in the NCIB's individual reports on each charity. These are free for the first three; otherwise, there's a nominal charge. Similar help is available from the Philanthropic Advisory Service of the Council of Better Business Bureaus (703-276-0100).

If your charity is purely a local operation, evaluations are tougher. It's possible to find out any negative verdicts by contacting the local consumer protection office, Better Business Bureau, or state regulator (in Maryland, this is the Charitable Division in the Secretary of State's office; in D.C., it's the Department of Consumer and Regulatory Affairs; in Virginia, the Division of Consumer Affairs). If there have been complaints, these offices should know.

An alternative approach involves asking the charity for a copy of its Form 990. These are open for public inspection; in fact, the organization is required to keep a copy on file in its home office. (You can also get them from the IRS itself or, sometimes, a state charity-registration office.)

However, NCIB director of public information Daniel Langan notes that "most people have enough difficulty filling out their own tax forms, let alone reading someone else's." He concedes "it's harder to get definite financial information on a local charity," and that the best advice remains common sense: Never commit to giving over the phone; whenever necessary ask for more information, including the exact number of homeless they feed or whatever it is they do; and don't be swayed by free trinkets that arrive in the mail. Finally: the best way to find out if it's a worthwhile organization is to volunteer your time.

As for those outfits that are out-and-out scams, most experts agree that these are only a minuscule percentage of the hundreds of thousands of charitable organizations. But Mackey points out that you're likely to encounter them to an extent all out of proportion to their numbers. "They're trying to make a buck, so they're calling and blitzing everyone," he says. "You'd better watch out."

For a brisker, take-no-prisoners approach than either handbook, it's necessary to turn to the July/August 1989 issue of The Other Side, a Philadelphia magazine that defines itself as "an independent, nonprofit, ecumenical magazine for Christians who take seriously the upside-down ways of Jesus."

The 123 charitable organizations profiled range from the National Abortion Rights Action League on the left to National Right to Life on the right, but largely fall on the liberal/radical end of the spectrum. They also tend to be smaller outfits.

"Uncompromising" and "colorful" are appropriate descriptions of the magazine's opinions. A typical comment: "The bulk of its work ... is the aggressive distribution of junk mail, soliciting funds for more junk mail ... You'd have to be absolutely bonkers to give {it} a penny."

One striking thing is how few groups offered the magazine information about the composition of their board, salaries or relevant financial data (in the case of the last, a test request was also made in the name of a private individual).

The National Resources Defense Council, for instance, is taken to task for telling The Other Side that its salaries are confidential. "So were Jim and Tammy Bakker's," is the response. "We suspect it uses outrageously high salaries to attract the superb scientists and lawyers it has on its staff, but as a publicly funded organization, it ought to have the guts to tell the truth about what it's doing."

That's nothing compared with the charges leveled against another prominent environmental group: "With imaginative flair, {it's} direct-action confrontations bear witness to real and potential ecological disasters. Unfortunately, it's fund-raising methods and use of money are among the worst around ... It's a poor team player and joins environmental coalitions reluctantly. Sometimes it raises money for causes it's scarcely even working on."

A more general piece of advice from the magazine: "We doubt that any organization that won't tell the public what it's doing with the public's money deserves any further financial support." That's a conclusion all the charity watchdogs can endorse.