From what I can remember I think there are two questions on the GCSE paper. The first you have a choice of three questions whereby you can chose either;
Writing to describe - 'Describe a school in the day and in the night’; 'Describe a journey you've had' (usually basic questions, very often contrastive)
Writing to persuade - 'Write a letter persuading your head teacher to offer an adventure-based holiday'
Writing to advise - 'Write a magazine article advising readers to eat more healthily'
As for the second question, I vaguely remember it being something to do with comparing texts; one is usually quite visual and includes a considerable amount of graphology, whereas the other tends to be more text/information based.
Do past papers.
Don't just complete every past paper make sure u know what each question is asking for.
Other than that I don't know much.
I wasn't really expecting to get an A I thought I got a D because I didn't complete last two questions which were the worth the big marks.