The best way to prepare for Paper 2 in German is to be aware of what will be asked from you during the exam. During the paper, which is 1,5 hours long, you will have to write one creative assessment (250 to 400 words). You get five options to choose from. The task often demands to write either a newspaper article (Zeitungsartikel), a diary entry (Tagebucheintrag), an essay (Aufsatz) or a letter or email (Brief oder E-Mail). Overall, grammatical accuracy and spelling is important, but it is also crucial to pay attention to your layout and style. Here is an example:
If you choose the option to write a diary entry, you will have to follow the literary style and layout of a typical diary entry. First of all, you will have to put a date, for example: Montag, den 14. Oktober 2013. You would then begin your diary entry with "Liebes Tagebuch" and finish it with "Dein/e ___". Diary entries are typically written in first person narrative, and in regard to style, you will be expected to use emotive and imaginative language. On the other hand, assignments like the newspaper article will require a more objective and factual description.
Familiarise yourself with these different formats so that you can apply them easily during the exam. I also recommed going through past papers to get an understanding of the language used.
When you sit the exam, make sure you read through all of your options in order to figure out which one suits your strengths best. When you have chosen a question, do not start writing straight away. Read the assignment carefully and highlight key words. Then create a detailed plan that shows your structure and your main arguments/ideas. Then nothing stands in a way of a successful exam!