Transworld Skateboarding has useful information stating some of the best methods.
https://skateboarding.transworld.net/features/how-to-get-your-city-to-build-a-skatepark/
Below are some other suggested links:
Tony Hawk Foundation: www.tonyhawkfoundation.org
Skaters For Public Skateparks: www.skatersforpublicskateparks.org
Skatepark Association of the USA: www.spausa.org
Skatepark.org: www.skatepark.org
olliecrankskatepark 