I did....oh.... 3 minutes at about 7:55 in the morning before the exam for each subject?
I wouldn't recommend doing it, i turned up to my maths exam thinking it was physics....still, at least i had my calculator on me and i was on time. I managed to still pull the A's out the bag.
My friend - who got a mention in our paper for outstanding grades in her GCSE examinations did an entire mixture for each subject. One of her best pointers....and i REALLY recommend this...is to put post-its everywhere.
Highlight. Bold. Colours...lots and lots of colours.
Put them on your desk, your windows, your mirror, your tv, walls, laptop...anywhere you go or will see (maybe keep them inside your room if your family dont want a sticky covered house)
making the post-its in itself is revision. You have to research what you are going to write and what you should learn - then go through your notes.
Then you also have the added help of your mind taking in the information as you walk around - like when a book has stayed upturned on a desk so long you can remember the reviews next to the blurb on the back off by heart. It's the same principle.
But one thing.
Don't stress out. I'm now doing A levels in English, Maths, Sociology and Spanish. Not a single one of them even looks at my GCSEs now, i'm 6 months passed my results and already they're practically forgotten.
They aren't the be all and end all of your education. If you're doing further education, they are in fact only a stepping stone to the higher qualification. They mean barely anything afterwards.
Best of Luck.