The best runners realize that it's not just the training that makes them great. Nutrition and sleep are mandatory to become a good athlete; there is no room for error.
Basics: Knowing about good nutrition is extremely important for athletes, especially in this era of misinformation. In the modern era there are so many diets out there (low-carb, gluten-free, fat-free, organic, etc.) that it's difficult to know what is actually good for you and what to eat.
In general, you will eat more when you are training - it's a basic fact. You are using more energy, so you need more energy (think about 2300 calories as a minimum, probably from 2500-4000 based on the individual). Here's the truth about many diets: they only help you lose weight by starving you. Eliminating carbs, protein, fat, dairy, etc. from your diet can be dangerous and unhealthy - this is why I do not suggest adopting a strict diet unless your body requires it. Instead, just focus on eating healthier - lower amounts of sugar, grease fat, and processed food, while including much higher amounts of whole grains, healthy fats, and fresh food. Try to eat fruit or nuts instead of candy for snacks, fresh or frozen rather than canned vegetables at your meals, and make sure you eat vegetables, carbohydrates, calories, vitamins, protein, and some fat in your meals - all are necessary for athletes. Eating sugars, unhealthy fats, fast foods, etc. are definitely fine to eat once in a while, just don't make it a habit. Most high schoolers unfortunately eat a ton of junk food - if you eat a lot of junk food, don't be surprised if your muscles feel like junk while training. However, remember that you need to not just replace the junk food with healthy food, but also eat more in general while training.
See these documents for more information:
If you have more questions, ask the coaches or contact Marcia Christiansen (contact information given below).
For nutrition advice: contact Marcia Christiansen, Registered Dietitian: firstname.lastname@example.org
Races, Workouts, and Post-Workout Meals
In the days and hours leading up to workouts, make sure you are eating plenty of good food and drinking liquids. Pre-race or pre-workout meals will vary from person to person, but in general eat something simple that won't upset your stomach and will make you feel fresh and good during a hard effort. Most of the nutrients your body needs for running fast are absorbed in the days leading up to the race, so just eat something healthy. Don't eat a large meal within 3 hours of racing, but smaller meals and snacks are okay. Drink water, sports drinks, or something else light in the hours leading up to the race. I usually mix fruit juice with water and put in just a pinch of salt or pickle juice to help the body absorb the liquids.
Post-workout or post-race, get fluids into your system immediately. Also important are protein and carbs to help rebuild your muscles - granola bars, fruit, nuts, yogurt, and other foods within 20-45 minutes, followed by a full meal within a couple hours (unless you have another race that day, in which case eat some fruit, nuts, and other small items immediately after racing to restore your energy levels).
Some nutrition information
Protein: Protein is necessary for building and healing muscles, and is thus necessary for any athlete. This does not mean you have to eat meat at every meal or even every day - almost all food contains some protein, so just eat a variety of foods. Some good sources of protein: meat, eggs, edamame, peanut butter, fish, soybeans, lentils, broccoli, peas, nuts, milk, cheese, yogurt, hummus, etc. Mix and match for full effect, and try to get both carbohydrates and protein into your body after any workout (a 4:1 ratio of carbs to protein is best). Studies have also shown that eating/drinking some protein before sleeping encourages muscle repair and development. Athletes need more protein than most people - aim for 50-80 grams/day.
Carbohydrates: Carbohydrates are used to create glycogen and maintain blood glucose levels, which powers your body. This means that they are also necessary for a runner in training (otherwise you won't have any energy!). Just make sure that you include foods with nutrients as well as carbohydrates: whole grains, potatoes, rice, breads, fruits, vegetables, and many other foods. Carbohydrates from foods like candy and soda, while fine in small amounts, really don't help you much nutritionally at all. If you are craving sugar, aim for more natural sugars like fruits and fruit juice, but don't be afraid to eat a few cookies now and then. Try to get both carbohydrates and protein into your body after any workout (a 4:1 ratio of carbs to protein is best). For more info visit CDC Nutrition.
Organic: Eating organic can be helpful and healthy, so go ahead and spend the extra money if you wish - although it is not necessary. If you don't want to eat organic, just focus on eating more fresh or frozen fruits and vegetables, as well as fewer processed foods.
Supplements: Many supplements are not regulated by the FDA, and thus may not actually have the ingredients claimed on the label. However, it is suggested that athletes (especially females) take an iron supplement daily as endurance training requires higher levels of iron. Take it with food - vitamin C helps the body absorb iron, while calcium prevents it, so take it with orange juice but not with milk.
Hydrogenated Oils: One of those things that show up in a number of not-so-healthy foods. In general, hydrogenated oils are a chemically modified oil used to improve shelf-life of food. Unfortunately, the oils also act as fat in your food - and while some natural fats are necessary for your health, your body doesn't know what to do with hydrogenated oils and other similar processed fats. Recent awareness of trans-fats has decreased the number of foods with hydrogenated oils in grocery store shelves, but in general, read the label and eat as little of food with hydrogenated oils as you can.
High Fructose Corn Syrup: Used to sweeten various foods and drinks - try to limit how much of this you take in (careful, it's in almost all soda and a number of fruit juices as well - look for those without). Once again, okay once in a while, but don't partake every meal.
Vegetarian: If you want to eat a vegetarian diet due to moral concerns, that is understandable. Realize that you will have to work harder to eat enough iron and protein (go for a variety of sources like lentils, beans, and dairy), as well as making sure you get foods fortified with vitamin B12 (a necessary vitamin mostly found in animal products). It is not impossible to be both a vegetarian and a good athlete, but it is more difficult.
Gluten-free: While eating gluten-free is necessary for those with celiac disease or a strong gluten intolerance, don't make the mistake of thinking that it is a necessary part of a healthy diet. Gluten is simply a type of protein - it is not harmful to your body unless you specifically have gluten problems. However, it may benefit you to limit or eliminate gluten in your diet if you are part of the 1-3% of Americans who have celiac disease or a strong gluten intolerance: http://www.huffingtonpost.com/layne-lieberman/glutenfree-revealed_b_5345917.html
Don't trust me? See what the NCAA says about nutrition.