I think what is best is a frank discussion with each pupil at the start of the course about what you expect and how much work is required to get each grade. The main problem with 'pulling them through' is that at university they will flop badly because of never having had to take the initiative. There was a very interesting video a few whiles ago, speaking exactly about the two types of pupils that take A-levels. The basic premise is you have kids who learn no matter what you do and then kids who only learn what they believe is relevant at any time. Basically use module tests and structuer the questions exactly like they will be doing in lessons. My favourite is to set 10 question module tests and at the end of each 3 lesson run give a set of 4 questions, one of which will certanly be on the test. It is very difficult to learn by heart 40 questions but it's not so difficult to work throguh them. This shows the pupils the link between work and grade, this isnt always so obvious to the kids. I use this 10 question and 40 question idea with a few classes and it really motivates the students.