GCSE english

Honestly, I would go over your books that you have been studying, re-read them and go over your notes from school, then do some past papers, make some flashcards, mind maps and maybe go over to a friend's house and study together. I'm sure you will do just fine if you do the above.
Good luck!

Ok, go through SPaG and make sure it's perfect(you don't want to lose any unnecessary precious marks there!)
Improve your vocab, if you have time to read, if you are in a hurry download some vocab online- Tiny Cards are a great resource that you can tap onto your phone.
Write a diary, writing will improve... well your writing, by doing this you will make fewer mistakes during tests and it is a great resource for going over what you have learn on the day.
Dude, honestly that's all you have to do, practice makes perfect!
Any more questions just shout!