My best tip is not to worry too much. If you can try and give one good example from all the main tenses (present, past perfect/imperfect, immediate future/future, conditional and maybe one sentence from something fancy like the subjunctive), throw in a couple of idioms and lots of opinions and reasons, you're well on your way to an A*. I passed out for a couple of seconds in my german oral, and I still came out with a good grade!
Best revision tips I can offer:
-Hold conversations with yourself in the language.
-Tape yourself and play it back, this also helps improve your accent.
-If you go to the doctor or the shops or anything, think to yourself "How would I have asked for that in spanish/french/german etc?"
-Try and talk to your parents or whoever in the language, give them a copy of the questions, and even if they don't understand or if they ask you the question in english, it will still help you.
-Most importantly: Don't Panic! Relax, stay calm, revise hard, take regular breaks, and you're on your way.
Good Luck!