Come by the day of class around 3pm and sign-in on the stand-by list. There's a good chance you will be accepted.
To limit the amount of "groups" (mostly the kind that doesn't eat meat, for instance) registering and filling up classes, the State Hunter Education Program limited registrations to two-months out. A second, mid-week class was implemented to take overflows from the prior week's weekend class.
To cover all bases, I'd recommend trying to register for the weekend class, and if it's full, register for the weeknight class, if that's full, come stand-by regardless to get in early. The class sizes are more regulated than they were three years ago.
Hope that helps, see you in class.