NSDA is the organization responsible for governing most national level debate and determining monthly topics for Public Forum, Lincoln Douglas and Policy. Their website has a lot of great resources. It is recommended that you read the rules and regulations regarding any events you are competing in.
CHSSA is the organization responsible for running the state tournament. It is recommended that you read the rules and regulations regarding any events you are competing in.
SDIVSL is a subset of CHSSA, responsible for running the local league tournaments.