Okay, students - want to ace your next exam? Here are tips for studying and test-taking from psychology professors, sleep-experts, and university researchers around the globe that were compiled by The Wall Street Journal: First: Don't just re-read your textbooks and notes, and memorize facts. Focus on broad concepts, too. For example, for a test on the digestive system, practice explaining how digestion works from start to finish. Because having a better grasp of the overall picture makes it easier to retrieve the facts. Also: Test yourself. Because that trains your brain to retrieve the knowledge from memory. For example, one student took 30 practice SAT tests - and saw his actual SAT score jump 50 percent. Why? Because setting up timed tests helped him learn to pace himself, and seeing his scores gradually get better boosted his confidence. Another tip: Use your sleep wisely. The night before the test, review the toughest material right before bed. Because while you're asleep, your brain will re-organize what you just learned - making it easier to recall the next day. And skip the all-nighters, which have been linked to lower grades. In fact, just one all-nighter can impair reasoning and memory for four days. What you eat is just as important. For example: Your best pre-test meal is a salad topped with chicken, a hard-boiled egg, and vinaigrette dressing. The chicken and hard-boiled egg contain energizing protein, and the oil in the dressing will help slow down digestion - stabilizing your blood sugar levels and keeping your energy levels high. DON'T have a bagel. MIT researchers found that people who ate a high-carbohydrate foods had high tryptophan levels. Tryptophan is a sleep-inducing amino acid. The bagel eaters had tryptophan levels that were four times higher than people who'd eaten a high-protein meal.