There 's so many different things I would have liked to know before my first trip but i always think that until you have actually been, no matter how well it is described, you can never actually imagine how great it really is.
Seen as im from the UK and we dont really have hot sunny days, i would have liked to know how hot, humid and exhausting it can get throughout the day.
Also, how fastpass is the best option because it really speeds up the queueing process (we visited three times before we used fastpass) and once we had tried it, we wished we'd used it before.
Finally i would have liked to know that the parks close earlier during off-peak season. We didnt realise this when we visited last October and it was quite disappointing.
Hope ive helped!!!!!!!!!!