Practice, practice!
Practicing questions is paramount and indeed the only way to study maths. Try to do as many questions as possible, the more difficult the better. I also think it’s a good idea to take note of the most difficult questions you come across and treat them as ‘benchmark’ questions. This is a good way to identify any weaknesses you may have and work on them.
Work hard & smart!
Working both hard and smart is essential in order to achieve a H1. When you reach the end of a question think logically and ask yourself if your answer is reasonable. You may even cross check it by subbing your answer into an equation or using an alternative method to get the same answer.
Read the paper fully before starting
In the exam, read through the paper fully before starting. A lot of questions are ‘scaffolded’, meaning that one part leads to the next with incremental difficulty, so reading ahead gives you an idea of what they’re looking for at the start.
Also, spend a minute or two on the questions you think are most difficult at the beginning of the exam. Simply reading through them a few times means they will be in the back of your mind and you will more than likely have a better grip on them when you attempt them later.
Know your theorems, constructions & definitions
Finally, know all your theorems, constructions and definitions. There is no choice on the paper so it is definitely worth your while to learn these.