Get there when the gates open.
Go straight for the ride you want the most, and get it out of the way before the queues build.
The queues also die down right before closing time (if you can keep going that long).
Good place for food is the all-you-can-eat pizza/pasta/salad buffet place in the Market Place. Or bring sandwiches.
And have fun! There is loads to do even if you don't want to queue for the top rides - don't forget the shows and the zoo.