OK, I'll donate, but that was a s***ty way to ask
I have to do it all the time. I prefer asking for biger dollars from fewer people so I usually go to friends who own businesses and ask for a contribution. For the smaller stuff, I rotate. This person hears about Girl Scout Cookies, this person about Boy Scout Popcorn, this person get's the High School Tennis Team stuff, etc.
Effectively? Do not worry about effective, just keep asking people. Play the numbers like a mutual fund.