Drink loads of water throughout the day. At least eight glasses (1.75l) a day, or you'll be top candidate for dehydration. Dehydration slows your thought processes down. You may get headaches. You feel knackered.
Cut down on caffeine. Great for occasional emergency late-night revision but not all the time. Overdosing on coffee, tea, Coke or energy drinks messes with your brain. You can't focus. It whacks up your heart rate, stops you sleeping and makes you feel doubly nervous and shaky before you've even started. So, no more than four cups of instant a day - and decaff only after 6pm.
Eat breakfast. Not necessarily a full English breakfast and not heavy but something to keep you going all morning. How about eggs done any way, porridge, a yoghurt and banana mix, or a brain-boosting blueberry and raspberry smoothie?
Keep up the vitamins. Treat yourself to healthy juices, smoothies and stress-busting tea to boost your immunity to colds and chill out your nervous system. Ginger and lemon tea is good if you think you're going to throw up.
Eat feel-good and brain-boosting foods. The tryptophan in chicken, turkey, fish, cheese and eggs is part of a protein that triggers off the feel-good serotonin in your brain, while the iron in egg yolks, green vegetables and beef helps oxygen get to the brain.
Eat omega 3s. Ultimate brain boosters. Find them in oily fish such as salmon, fresh tuna, mackerel, sardines and anchovies. Snack on the right stuff. Such as dips and crudites, a tasty wrap or sandwich, toasted fruit bread and peanut butter.
Eat tactically on exam days. Breakfast, of course. Nothing too heavy before an afternoon exam - you'll get dopey. Take really light food before an oral and no coffee - it dries the throat and makes you more nervous. No dairy - it clogs up your throat. Sip water before you go in. Sit and do some light breathing exercises Sam Stern passed 10 GCSEs at grade A last summer and is now beavering away towards AS-levels. These tips are taken from his bestselling first book, Cooking up a Storm: the teen survival cookbook, published by Walker books, priced pound;9.99. His third book will be published in October