This is my take on the topic:
In most cases, if you want a H1 enough then you'll get a H1.
Of course it depends on the subjects you do, for example I found my arts breadth subjects were significantly harder than my science subjects because they didn't really come naturally to me.
For science subjects there are heaps of resources that will help you out. For example, for chemistry you have:
- 2 different textbooks and each contains chapter review questions
- Access to practice exams (about 6)
- Tutorial questions from your workbook (those are the sorts of questions you have to master before the exam in order to do well)
However, keep in mind there will be subjects where you DON'T have access to practice exams. Some subjects will only give you a 'sample paper' to give you an indication of the 'types of questions' that will be on the exam, for example Biology. For most subjects though, there will always be readings (which are designed to give you a better understanding of different topics covered in the lecture notes, keep in mind the content of the lecture notes is what is examinable) and often they do contain questions and questions from your tutorial workbook.
I'm pretty sure there is some sort of scaling that occurs for end of year marks though, so that's also another reason why students who do the most work tend to perform quite well in comparison to others (in most cases, other times you just get lucky)