Some state Fish and Game departments offer advanced hunting classes that are designed for people who already have taken their hunter Safety class and have a hunting license. I don't know of any formal hunting classes (like at a college or something) as OT mentioned. There are lots of books, magazines and online articles that will cover many of the basics and some useful tactics for hunting. You could also search this website for different topics that provide a lot of tactics, methods and other useful information. Is there a specific animal or type of hunting you're trying to learn more about?