I have never joined and always find a way to get the credentials I am wanting.
It all involves pre planning. Most people handing out the credentials have no idea what a fancy IFPO is, or any other membership for that matter. Tell them you are an LPC accredited Photojournalist! To them, same thing.
Let me know your secret..I use to shoot all kinds of sporting events around here but now it seems like it has all ran dry. I you could give some advice I'm all ears.