@coasterBroOkay, do Blue Fire and Alpenexpress first, they get the longest lines. I'd also suggest the Tyrolean log flume - but you can get very wet there, and you might not want to early in the morning. Using the early opening for Pirates in Batavia is not really necessary as it has a huge capacity and only gets long lines on very busy days.
You can, of course, as a hotel guest take EP Express to the main entrance where the "normal" guests have their early opening of Voletarium and I think the attractions in the Italy area. You can get a return time ticket for Voletarium and try to get in a good rope drop position for Silver Star. But I would not recommend that - enjoy the quietness of back area of the park instead.
I'd suggest trying to get into Arthur or Wodan next, then maybe one of the water rides early before it gets warm and people decide they need refreshment.
Hidden gems...definitely visit the garden of Balthasar Castle in the German area. Also, Snorri Touren is a cute little dark ride and in Ireland the Dancing Dinghie is quite fun. Also don't miss Pegasus, it's a "family coaster" and quite short but fun.. And Kassandra's Curse, a quite unique mad house.
Food in the park: skip the usual burger, sausage and fries stands. You can get that anywhere and it's not that great. Try Bamboe Baai or Spices for exotic flavours or Restaurant Castle Balthasar or the beer garden for some authentic German food.
Water Rides: the log flume and Fjord Rafting can be wet (though not nearly as wet as River Quest in Phantasialand). Atlantica and Poseidon are usually quite tame.
Virtual Line: all rides included in Virtual Line have both standard and virtual queues. Pirates and Euro Mir merge the lines at the entrance to the building and the others have completely separate lines up to the ride (they use the former Single Rider queues)
All lines are usually open until closing time, and the rides operate until the queues have been emptied. You won't immediately get kicked out at closing time; gift shops may be open for some time even when the park has officially closed.
Oh...try to get the last ride at Alpenexpress. You may get three, four or even more laps instead of the regular two.