It's a combination of hard work, natural ability and logic.
i agree with the natural ability (for me that is) - my sister did her masters in maths and she showed me the amount of work she did during a levels and lol it was a ridiculously huge amount hahah lol but she said she worked really hard for it and ended up getting A* for maths and A for further maths.
Does anyone have any particular exam technique that have worked well for them for maths papers?
Read through all of the questions before you start because then your mind subconsciously thinks about how to answer the questions, even when you're doing a different one.