When I visit Alton Towers, I always go to Nemesis first(YES Believe it or not, I always avoid Oblivion first, I will tell you in a min) Nemesis always has a short queue for the 1 hr when the park opens and is infact nearly always a walk on. I then go over to Oblivion for the 1.30PM Trick, I do this because Crowds in X-Sector die down about then, and Oblivion is no more than 10 mins long.
At IOA when I went twice in 1999, I always went straight for the Hulk first, I was'nt meant too I wanted to go to the back of the park, But when I saw a train launch out of that tunnel, It was an amazing site, and I just had to do it.