Really what you should be doing is as the first poster said, summarising class notes before you go to sleep, briefly everyday or even on the weekends. I heard from a teacher that is was unwise to cram for subjects in senior years, because you get tested on the same stuff again and again and again in different tests. So you end up wasting more time cramming each time (and possibly not getting an ideal mark), instead of getting it right the first time and remembering that knowledge.
On the other hand if you prefer cramming, it is extremely important that you have a copy of the syllabus. You will be surprised at how much time this will save you. Ask you teacher what dot points on the syllabus are being tested in the test, and go home and make sure you can answer all those questions. Afterall, they cant test you anything that is not stated in the syllabus. The syllabus for science, is extremely specific, to the point where the dot points actually tells you what you need to know, and how you need to be able to process that information (i.e student is able to identify and explain blah blah blah). The points may sometimes suggest dot points which were covered briefly by your teacher in class, which you would've not covered if you were just reading the book. This which unfortunately without, you will have to go to the internet to find.
