Stuntman707

All tickets and discounts are sold through the Annual Pass building. Advance collections are the windows to the right of the entrance turnstiles. The kiosks are only used for security.

Usually Sundays are quieter than Saturdays so if you don't manage to get on anything on the Saturday, you should have better luck on the Sunday.
Another tip I can give is don't eat lunch between 12 and 1pm. You'll waste more time in long queues to buy food and it is the perfect time to try and get on the popular rides while everyone else is eating. Usually we have lunch after 1pm when we go.
Finally, if you see a ride has just re-opened after stopping for a while, run to that queue or as quickly as you can manage. Once the line fills up again, the queue time usually won't be that low again for the rest of the day.
 
Enjoy the island!

I'd say Fastrack is the quickest way to get on. If you're not with anyone, single rider is usually quicker than the main queue.
Unfortunately, the estimated queue times have not been accurate at all recently so I would go and have a look at how long the queues are in person.