Don't ask if you won't listen. Also, if someone gives you sound advice, and you act on it, it will be very difficult for them to say no, when you return and ask for a gift to support the initiative they recommended. Both include key ingredients for success. Make your gift first. If you are not committed to the cause for which you are soliciting support, you will not earn the investment of others.
Charity begins at home.
If you have not yet made your gift to the campaign, do it today. Write out a check for an amount larger than you think you could give. If you don't, then think twice about the merits of what your organization is doing, and whether you can justifiably ask others to make sacrificial gifts. State your case. Tell them what the project will accomplish, when it will get done, how you intend to finance it, how you will monitor its success, and what you would like them to do.