The most effective way of studying is doing questions (and a lot of them), and making sure you understand the concept and how you answer each questions (so that when you get into the test, you are able to answer all questions, no matter how it's worded)
In regards to 'How many hours a night should I be studying?'
- It all comes down to how efficient your study is. You could be doing many hours a night, however, it could end up being pointless study.
In my opinion, you do not need to be studying every day in order to get the top marks (as some days you'll have other stuff planned, low energy levels etc)
Hope this helps