You don't have to start with a full exam. Tackle it in easy stages.

Take one question from a past paper, and see how much you can write in the time allotted.

If you do this at school, it will be organised for you. But you can also do it on your own.

Try to create exam conditions by being alone in the room.

Time yourself, and remember that there's no point in cheating.

You can write whatever you wish. Nobody will see the result except you.

If it's no good, you can do it again. In fact, you can't lose!