Your congregation's mission or "vision" statement should be compelling. How contributions will actually be used should be common and public knowledge. If gifts are going to your endowment fund, prospective donors will want to know how their gifts will be invested and managed, how endowment earnings will be allocated for spending or re-investment, and under what circumstances, if ever, the principal might be invaded.
Tax savings are seldom the primary motivating forces for charitable contributions. In some instances, however, the tax benefits of philanthropy allow some individuals to give more than they initially thought possible.