Advisors who help clients with their charitable giving must think not only of charities and potential tax benefits, but the effect of such largesse on the client's overall portfolio. The impact of making a few large gifts may be quite different than the outcome from making many smaller gifts. Here are some tips to help clients decide how many charities to support:

1. How important is the cause? "The more passionate a client is about it, the greater the possibility a client will want to concentrate their charitable capital to affect one cause," says Joel Redmond, senior financial planner at Key Private Bank, in Syracuse, N.Y. This is the first and most important decision to make about a client's charitable giving, since it will guide everything else. "If they are truly passionate about one cause, then there is no need to spread the wealth,” says Jennifer Landon, president of Journey Financial Services in Ammon, Idaho.

2. Advisors should encourage clients to make a budget based on the impact they want to make, says Scott Shellhamer, managing director at Warren Financial in Exton, Pa. How clients plan to connect with one or with several charities will determine the amount they need to save.

3. Advisors should help clients compare the tax benefits of various types of contributions, says Redmond. If a contribution to one charity needs to be in cash, but another charity will take highly appreciated property, for example, those guidelines might determine the scale of the contributions to be made.

4. Consider the administrative impact. Marguerita Cheng, chief executive of Blue Ocean Global Wealth in Rockville, Md., says there's a valid argument to be made for either a smattering of smaller donations or a few large ones. Fewer, larger donations "help the charitable organization maximize their impact by minimizing expenses associated with fundraising," she says. "Other clients may like to support friends and family who participate in marathons or walkathons to raise money for charity."

5. Help clients determine whether different employers match charitable gifts, suggests Shellhamer. "In corporate philanthropy today,” he says, "many employers will match the giver’s donation. Most employers require that the organization be a 501(c)(3)." If a client is considering multiple charities, it might make sense to narrow down the list to include only those organizations that qualify for a corporate match.

Bruce W. Fraser is a New York financial writer and contributor to Financial Planning.