What organizations can help prepare you for a future career as a game warden?

Dear Josh,
Thank you for your excellent question. Game Wardens exist all over the country, some employed by the state and others for the federal government. So the exact requirements vary by each agency. There are some general points to bear in mind however:
Being a game warden is often as much about communications and networking as much as it is about being in the outdoors and working with animals/fish
Doing well in school, staying out of trouble, and keeping good habits is something that government employers will examine closely.
Visit any of the agencies' websites to learn more about specific requirements
One national association is http://naclec.com/; another is http://naweoa.org/
I hope this helps ;)