It's impossible to prepare for every question they may ask you. There was a phase a while back (not sure if it's still being done as much) for asking questions that are extremely unlikely to be answerable e.g. how many piano tuners are there in the UK. These questions are designed specifically to see if you can think on your feet, and the best answer I found was "I don't know off hand, but I could use x and y resources to find out".
The most likely questions will be based around the required skills for the role "give us an example where you did this, or where you applied that skill". So go through the job spec and think about tasks you have done that fit those requirements - doesn't have to be a different example for each one!
Make sure you have your clothes etc laid out tonight, stuff like spare tights, tissues etc - nothing worse than going in feeling unconfident because you have a large ladder in an obvious place
. Leave contigency time in place, if you get there a bit early that doesn't matter.
You might try sniffing lavender before you go in, this can have a calming effect. The first time you feel yourself panicking in the interview stop, apologise and explain you are rather keyed up because this new job would mean so much to you. Don't feel you have to launch into words as soon as they finish asking you a question, you should be able to take a few seconds to compose yourself & make sure you have the right answer clear in your head.
And lastly, don't look on this as the be all and end all. Try to think of it as just practice.