The guide lists what may not be open at any given time. It's more complicated than it should be, but only when people complain enough to City Hall will it get changed back. This happened to us on more than one occasion, where we were given an old guide for Thursday when it was already Friday or Saturday. Lucky us, we noticed right away that Fantasmic wasn't scheduled on the guide we got, so we were able to figure out the problem pretty quickly. Keep checking the postings on the board so you can plan for minimal wait times.
Lines only grow longer for the mountain range as the day goes on.
It's a well known fact that your eyes tend to close up with bright sunlight. If the line ends right at, or inside the entrance door, you have about a 20 minute wait, perfect for taking in all the detail in the pre-show area. After visiting the hotel, you can board the monorail there to return to Tomorrowland. It's a nice way to peek into the park without having to pay for the whole day. Tickets are sold only at the hotel ticket booths.