If you are interested in any of the MHE classes and can't register for the class, you have a good chance of getting into the class if you show up early with generics and politely ask the instructor to be on the waiting list. Oftentimes, you can get in because someone doesn't show up or the instructor has enough materials to include an extra person or two.
For the last few years, my beginner classes have sold out during pre-registration, but for about 50% of the classes, I've had at least one no show.
Thank you, that's good to know! Last year was my first GenCon and there were so many events I wanted to do, but I wasn't able to get all of them. Still, when I couldn't get something, I would find something else. So given that I wasn't 'guaranteed' a spot, I had other events planned, which would have made it difficult to gamble with generics. I was tempted to drop into the Saturday night session, since I had no plans and figured that in the evening people might not show, but then I unexpectedly made it into the NASCRAG finals (it was a shock, since I had never played before and I had gone with a 'pick up' team) and suddenly Saturday night was taken!
But I will definitely keep your words in mind if I am unable to get into a beginner painting class this year!