Be a smarter charitable giver

(Money Magazine) -- When it comes to charitable giving, some well-intentioned moves can backfire.

Here's how to make sure your donations have the biggest possible impact, whether you're giving on a large scale or a small one.

Don't be swayed by a pretty face. You like to think you give money based on the worthiness of a cause, but less elevated emotions are often involved. According to a 2005 study led by economist John List at the University of Chicago, people are far more likely to give when a fundraiser is an attractive woman rather than a plain Jane.

What does this mean (other than that charities should immediately recruit former "America's Next Top Model" contestants)? Select charities by researching them yourself (charitynavigator.org is a good place to start) and give the hottie a gentle turndown.

Focus your support. Charities spend a bundle trying to find new donors. It's far more cost-effective for them to rely on generous repeat donors who are already in their database. For your dollars to do the most good, concentrate on one or two charities year in and year out rather than making smaller, scattershot gifts.

When your gift is a one-time thing, say so. Let's say you sent $50 to a disaster-relief organization in the wake of yet another California wild-fire. If you're not planning to write that charity any more checks, you might be hurting it rather than helping it.

That's because you're now on the charity's mailing list, and it may well spend more than $50 beseeching you for more money in the years to come. Do the right thing: Ask the charity to delete your name.

Tyler Cowen is a professor of economics at George Mason University.