Purchase or rent 20 to 50 plastic lawn flamingos. While you can sometimes pick these up in discount stores, there are many online retailers that offer bulk lawn flamingo sales and rentals. Keep in mind, though, that you will be planting these flamingos in lawns throughout your city. In all likelihood, you will lose some due to theft and transportation mishaps. If you rent your lawn flamingos, you will be responsible for their safekeeping and return, and it may be cheaper to purchase your own.
Announce the "Flamingo Flocking Fundraiser" to your organization. Create a list of people who wish to either be flocked themselves, or who wish to have the flamingos land on another person's lawn. Charge a flat fee or accept donations for the flocking.
Write a ransom note in your best lawn flamingo penmanship. You might announce that the birds are touring your fair city gathering donations on behalf of a local cause or charity. Or consider a more threatening tone, demanding immediate payment of $20 before the flamingo-pirates leave the lawn. If the ransom is paid, the garden gnome gets to keep his life, and the "donor" gets to pick the next victim.
Announce sightings of the flamingo flock throughout your organization. Be sure to snap photos of the lawns before and after the flocks hit. This is something that will keep people laughing for a long time, so have fun with it.
Continue this process for a predetermined time. One to two weeks will allow you to maximize the number of flamingo flockings while still allowing people to enjoy the novelty of your flamingo flocks.
Announce the total raised throughout the pink flamingo fundraiser to your group or organization. Pack the flamingos in a box, or sent them migrating back to the rent-a-flamingo store from which they came.