(MONEY Magazine) – What could be easier than taking care of your charitable obligations through a workplace giving program? Having your employer pull a few dollars from every paycheck is a pretty painless way to avoid looking like the office Ayn Rand. Americans donated $3.7 billion to charity last year through such campaigns.

But the campaigns themselves are getting trickier. The United Way is still the most frequent sponsor; but increasingly, companies are adding alternative groups modeled after the United Way's "mutual fund of charities" approach, such as Earth Share and the Independent Charities of America. You may also be able to donate to a specific charity via a payroll deduction. So if you face such a battery of options, here's what you should consider:

What are the costs? The United Way's cut of donations ranges from 10% to 20%, depending on the region. Alternative fund-raising federations slice off anything from 1% to 20%. If you're donating to a general fund, which the federation doles out to members, this is a fair price to pay for fund-raising and distribution costs, says Daniel Borochoff, president of the American Institute of Philanthropy, a Bethesda, Md. charity watchdog. But if you're designating a single charity, it will probably get more money if you donate directly. Plus, if your company says it's picking up campaign costs, that probably means in-house expenses such as handling the payroll deduction, not the federations' overhead.

How are members chosen? At a minimum, most federations require member charities to spend no more than 25% of their income on fund raising and to keep no more than three years of cash in the bank. Beyond that, scrutiny is limited in most cases to broad program screens, such as social services (the United Way), women's issues (Women's Charities of America) or environmental causes (Earth Share).

Can you choose your own recipient? For a specific charity to receive your donation, it usually has to meet the umbrella group's criteria. Even a nonprofit school might not qualify. If that happens, your donation could end up in the general fund. So check first with the federation.

--BEVERLY GOODMAN