When you pick up your badge holder at the show you will also get a book listing all the exhibitors and seminars.
if you wait some class you want to take may be full...
I would look into it now, get an idea what you want to attend, see if they require preregistration or fees. Some seminars that I want to attend confilct with another so I have been looking to see if it's offered more than once (which a lot are) and if they aren't then which one do I want to attend the most or would be the most beneficial to me.
have fun!