RE: 2008 NTC Lake Oahe June 13-14
It's an invitational championship.
All the qualifiers fished tournaments circuits this past year that were each given so many spots towards the National Team Championship.
Those that did the best points-wise in each of these circuits were given the invitations.
They probably have a list of circuits on their site that will let you know which ones are qualifiers for the NTC.
It's too late to qualify for the Oahe event, but you could see what you can do about qualifying for the 09 event. :)