Find the places where people have time
By finding places where people have the time to be introduced to new things, people will be educated, more interested in helping and spreading the word around.
People are often genuine intrested in helping people, but rarely consider themselves to have time for something new. To find the places where people have the time to get introduced to something new, eg information about donation (how to do it, how many we could save in a total effort and so on), would generate a more educated population. A more educated population would help spreading the word around and make people more aware of the differences they can make.
Example: metor newspaper: the tube/metro/underground use to be just a means to an end but with the newspaper Metro People got educated while "waiting" for something else. The newaper is free and is profitable due to advertisment in the paper.