dude, it's not just what you use, it's who's using it and how.
if you don't have them already, get copies of the syllabus for chem and go through the dot points - so many exam questions are almost word for word dot points.
and make sho that u completely understand each of those verbs in the list of verbs like 'explain' 'describe' and 'evaluate' and tht u no how to word all your responses correctly.
i think to get 90+ u should know ur stuff.. prove urself worthy of a 90.. everyone has a slightly different way of going about doing this, but the most common way is to do lots of practice