What we put into our bodies directly correlates to what we can get out of our bodies. Being mindful and intentional about the food we consume will provide optimal nutrition and sustained, energy. Keeping a log of your daily consumption is also a useful tool in maintain health - for weight loss, nutrition, hydration, and more.
There are lots of websites and applications to help you track your intake and your output: MyFitnessPal and LoseIt are set up to track your caloric intake with the added ability to track your activity, too. CalorieKing has similar features, but also has an extensive database for looking up caloric values of common (and uncommon) foods. Lastly, MapMyFitness is an activity-based program that allow you to track a wide variety of activities from ballet to gardening, sailing to yoga. You can also track food through MapMyFitness or link this program to any of the other calorie-based programs.