Make sure you actually understand what's going on. Your ~30 student can take any situation, and spit out mathematics that are relevant to what they're doing. A 35+ student should be able to actually understand what they're doing and why they're doing it. When you actually properly understand everything, then do practice exams.
When doing practice exams, don't just do one exam and be done with it. When correcting it, look at the methods used by the people who wrote the solutions. Then, think about other ways you could've approached the question - often, there is more than one way, and you might've picked the longer. In specialist, I learned much faster ways of finding derivatives of parametric functions by playing around like this, saved me a lot of time in the long run. In fact, particularly for methods, there are quite a few ways to answer questions, and often the technique used by most students is the more complicated one.
Finally, when it comes to a week before, DON'T LEARN NEW THINGS. You won't remember them - instead, just do practice questions and practice papers to hone the skills you already have. Learning new things that close to the exam will only scare you and detriment your score. In the week before, I tried to memorise the formula for the steady state solution, and I did not remember them at all.
Forming a group of friends you can go over things with helps - even in my case, I was miles ahead of everyone I worked with, but helping them out still helped me consolidate what I already knew. Plus, sometimes they found a quicker way to do something than I would've, so don't underestimate peers just because you normally do much better than them overall. While you might all be ranked against each other, you're also all in the exact same situation, so don't get so competitive that you're not willing to help each other out. In fact, I would've completely died in chemistry if it weren't for the friends I had to help me with the papers and revise with.