Lol, it's not even NCEA yet dude, just chill out.
You don't need to do exceptionally well on these exams. You just need to do well enough so you're allowed to do next year. Although, actually, I think some of my Level 1 classes were streamed (English and math) so it might be good to do well in them so you get in the top class.
And even when you get to doing NCEA the exams aren't incredibly difficult if you've done the work all year and you shouldn't need too long to review the material. Although you lot have a bit harder these days when people are actually differentiated when they get good marks from the people who just scraped through (I was the 3rd year to go through NCEA, which was the last year (I think) where if you got 100% E's and 100% of the credits or you got just 80 A credits you got the same NCEA Level 3 certificate).
Now after telling you not to worry too much since NZ high school is very, very easy. Tips for the exams, DO OLD EXAMS, DO OLD EXAMS, DO OLD EXAMS! This works exceptionally well in NCEA since often the questions are almost exactly re-used (works somewhat well at University, although I have been burnt a few times by studying too close to previous exams and then having most of the exam on stuff I perhaps glanced at in my notes but ignored since it wasn't in the previous 5 years worth of exams).
Other than that you can do other questions in textbooks, rewrite your notes (preferably summarizing them and not verbatim copying them from your text book)
I'd also recommend the studyit.org.nz forums, a lot of ncea discussion goes on there and some very smart people hang out there occasionally.
edit - Also, for English similar questions will come up for the essay questions each year (there's always one on theme for example) so you can sort of plan out your essay before hand (making it somewhat flexible so you can adjust it to fit the question).
Another good thing is trying to get some intuition behind why things happen in the subject. That's a bit hard to do with sciences since you don't start learning the truth behind things until university, however in math you can get an intuition for why this or that happens. (this type of intuition works very well for economics)
Oh, and someone mentioned highlighting (they also mentioned writing notes from that highlighted section which is good), highlighting can be sort of bad if you just go through highlighting stuff as it gives you false sense doing something and learning.