If this is your first GenCon, DON'T schedule yourself for ANY events!
Totally disagree with this. A small amount of planning will avoid the pitfalls freebie experienced. If you do have to go to will-call on Thursday morning (a stretch in Hell sounds more fun, but some people's schedules just work out that way), then don't schedule anything before noon on Thursday.
Even if you want to max out your Exhibit Hall time, the Hall is open from 10-6; that leaves several hours outside of that interval to fill. In fact, you may want to schedule an event or two in the middle of the day, just to get away from the crowds & insanity of the Hall.
Yes, you can find plenty to do with generics, but all the good/popular events will have sold out, and there will often be people waiting for space to open up. Search that event catalog, find games & other stuff you might be interested in, and sign up for them. There is True Dungeon, Escape Rooms, thousands of RPGs and board games, movies, seminars. To simply discount all events because of will-call issues is silly. You have 4 days, pack it with fun, and you'll sleep when you (or your characters at least) are dead. :-)