If your workout is the key to your dream physique, then your diet is the key to your most effective workout. The food you eat is directly tied to the way your body performs, and an under-performing body won't burn as many calories or build as much muscle as one that is perfectly fueled. Timing is important -- even the perfect meal can leave you flat if you eat it too early or weigh you down if you eat it too late -- but the most important factor is the mix of carbohydrates and protein.
The actual amount of carbs and protein you eat depends upon how much time will elapse before your workout. No matter what volume of food you consuming 5 grams of carbs for every 1 gram of essential amino acids -- about 1.6 grams of a complete protein will provide 1 gram of essential amino acids. Consuming these nutrients before your workout allows your body to take advantage of workout-induced increased blood flow to establish the amino acids in your muscles while boosting blood sugar for steady energy.
Obviously, the closer you get to your workout time, the smaller the meal should be. If your only pre-workout nutrition is a regular meal, eat it about three or four hours before you exercise so the food has time to digest. Otherwise, your full stomach will be susceptible to upset, and the nutrients won't be available in your bloodstream when your body needs them. Smaller meals can be eaten two or three hours prior, but stick to a small snack if you only have an hour to go. Whatever you decide to eat, keep the 5:1.6 grams carb-to-protein ratio in mind.
Supplements are by far the easiest way to ensure you get the proper ratio in an appropriately-sized food source. Many protein shakes and sports bars are designed specifically as pre-workout nutrition and have the precise nutrient ratio you need. They also have the added advantage of being portable, which can be convenient for those who hit the gym on the way home from work. If you are stuck without your favorite supplement at hand, fat-free chocolate milk will suffice since it provides the exact carb-to-protein ratio as a pre-workout shake. The fat-free part is important though -- fat digests slowly and can weigh you down when you least need it.
Supplements are simply convenience products, and are not necessary to good nutrition. You can get the same benefit from whole foods, but this requires more planning and label reading. Fat-free yogurt with fruit and granola works, as does a whole-grain bagel with peanut butter. For a larger meal, a turkey sandwich on whole grain bread with lettuce and tomato is a nearly perfect pre-workout meal, and bananas or fruit juice can be a last-minute snack for quick energy.